SQL Tutorial
Short Description
W3 SCHOOLS SQL TUTORIAL...
Description
SQL Tutorial 2/10/2010
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Table of Contents 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
SQL Tutorial ............................................................................................................................. 4 Introduction to SQL ................................................................................................................... 4 SQL Syntax ............................................................................................................................... 6 SQL SELECT Statement ........................................................................................................... 7 SQL SELECT DISTINCT Statement ......................................................................................... 9 SQL WHERE Clause ............................................................................................................... 10 SQL AND & OR Operators ..................................................................................................... 12 SQL ORDER BY Keyword ..................................................................................................... 13 SQL INSERT INTO Statement ................................................................................................ 15 SQL UPDATE Statement ........................................................................................................ 17 SQL DELETE Statement ......................................................................................................... 18 SQL TOP Clause ..................................................................................................................... 19 SQL LIKE Operator ................................................................................................................ 21 SQL Wildcards ........................................................................................................................ 23 SQL IN Operator ..................................................................................................................... 26 SQL BETWEEN Operator ....................................................................................................... 27 SQL Alias ................................................................................................................................ 28 SQL Joins ................................................................................................................................ 29 SQL INNER JOIN Keyword.................................................................................................... 30 SQL LEFT JOIN Keyword ...................................................................................................... 32 SQL RIGHT JOIN Keyword.................................................................................................... 33 SQL FULL JOIN Keyword...................................................................................................... 34 SQL UNION Operator ............................................................................................................. 35 SQL SELECT INTO Statement ............................................................................................... 38 SQL CREATE DATABASE Statement ................................................................................... 39 SQL CREATE TABLE Statement ........................................................................................... 40 SQL Constraints ...................................................................................................................... 41 SQL NOT NULL Constraint .................................................................................................... 41 SQL UNIQUE Constraint ........................................................................................................ 42 SQL PRIMARY KEY Constraint ............................................................................................ 43 SQL FOREIGN KEY Constraint ............................................................................................. 46 SQL CHECK Constraint .......................................................................................................... 48 SQL DEFAULT Constraint ..................................................................................................... 50 SQL CREATE INDEX Statement ............................................................................................ 51 SQL DROP INDEX, DROP TABLE, and DROP DATABASE ............................................... 52 SQL ALTER TABLE Statement .............................................................................................. 53 SQL AUTO INCREMENT Field ............................................................................................. 55 SQL Views .............................................................................................................................. 58 SQL Date Functions ................................................................................................................ 60 SQL NULL Values .................................................................................................................. 62 SQL NULL Functions ............................................................................................................. 64 SQL Data Types ...................................................................................................................... 65 SQL Functions ......................................................................................................................... 70 SQL AVG() Function .............................................................................................................. 70 SQL COUNT() Function ......................................................................................................... 72 SQL FIRST() Function ............................................................................................................ 74 SQL LAST() Function ............................................................................................................. 75 2
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
SQL MAX() Function .............................................................................................................. 76 SQL MIN() Function ............................................................................................................... 77 SQL SUM() Function .............................................................................................................. 78 SQL GROUP BY Statement .................................................................................................... 79 SQL HAVING Clause ............................................................................................................. 81 SQL UCASE() Function .......................................................................................................... 82 SQL LCASE() Function .......................................................................................................... 83 SQL MID() Function ............................................................................................................... 84 SQL LEN() Function ............................................................................................................... 85 SQL ROUND() Function ......................................................................................................... 86 SQL NOW() Function ............................................................................................................. 87 SQL FORMAT() Function....................................................................................................... 88 SQL Quick Reference From W3Schools .................................................................................. 89 SQL Hosting ............................................................................................................................ 92 You Have Learned SQL, Now What? ...................................................................................... 93 SQL Quiz ................................................................................................................................ 93
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1 SQL Tutorial « W3Schools Home
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SQL is a standard language for accessing databases. Our SQL tutorial will teach you how to use SQL to access and manipulate data in: MySQL, SQL Server, Access, Oracle, Sybase, DB2, and other database systems. SQL Syntax SELECT Company, Country FROM Customers WHERE Country 'USA'
SQL Result Company
Country
Island Trading
UK
Galería del gastrónomo
Spain
Laughing Bacchus Wine Cellars
Canada
Paris spécialités
France
Simons bistro
Denmark
Wolski Zajazd
Poland
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2 Introduction to SQL SQL is a standard language for accessing and manipulating databases.
What is SQL? • • •
SQL stands for Structured Query Language SQL lets you access and manipulate databases SQL is an ANSI (American National Standards Institute) standard
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What Can SQL do? • • • • • • • • • •
SQL SQL SQL SQL SQL SQL SQL SQL SQL SQL
can can can can can can can can can can
execute queries against a database retrieve data from a database insert records in a database update records in a database delete records from a database create new databases create new tables in a database create stored procedures in a database create views in a database set permissions on tables, procedures, and views
SQL is a Standard - BUT.... Although SQL is an ANSI (American National Standards Institute) standard, there are many different versions of the SQL language. However, to be compliant with the ANSI standard, they all support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner. Note: Most of the SQL database programs also have their own proprietary extensions in addition to the SQL standard!
Using SQL in Your Web Site To build a web site that shows some data from a database, you will need the following:
• • • •
An RDBMS database program (i.e. MS Access, SQL Server, MySQL) A server-side scripting language, like PHP or ASP SQL HTML / CSS
RDBMS RDBMS stands for Relational Database Management System. RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. The data in RDBMS is stored in database objects called tables. A table is a collections of related data entries and it consists of columns and rows.
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3 SQL Syntax Database Tables A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data. Below is an example of a table called "Persons": P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
The table above contains three records (one for each person) and five columns (P_Id, LastName, FirstName, Address, and City).
SQL Statements Most of the actions you need to perform on a database are done with SQL statements. The following SQL statement will select all the records in the "Persons" table:
SELECT * FROM Persons In this tutorial we will teach you all about the different SQL statements.
Keep in Mind That... •
SQL is not case sensitive
Semicolon after SQL Statements? Some database systems require a semicolon at the end of each SQL statement. Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server. We are using MS Access and SQL Server 2000 and we do not have to put a semicolon after each SQL statement, but some database programs force you to use it.
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SQL DML and DDL SQL can be divided into two parts: The Data Manipulation Language (DML) and the Data Definition Language (DDL). The query and update commands form the DML part of SQL:
• • • •
SELECT - extracts data from a database UPDATE - updates data in a database DELETE - deletes data from a database INSERT INTO - inserts new data into a database
The DDL part of SQL permits database tables to be created or deleted. It also define indexes (keys), specify links between tables, and impose constraints between tables. The most important DDL statements in SQL are:
• • • • • • •
CREATE DATABASE - creates a new database ALTER DATABASE - modifies a database CREATE TABLE - creates a new table ALTER TABLE - modifies a table DROP TABLE - deletes a table CREATE INDEX - creates an index (search key) DROP INDEX - deletes an index
4 SQL SELECT Statement This chapter will explain the SELECT and the SELECT * statements.
The SQL SELECT Statement The SELECT statement is used to select data from a database. The result is stored in a result table, called the result-set.
SQL SELECT Syntax SELECT column_name(s) FROM table_name and
SELECT * FROM table_name Note: SQL is not case sensitive. SELECT is the same as select.
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An SQL SELECT Example The "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select the content of the columns named "LastName" and "FirstName" from the table above. We use the following SELECT statement:
SELECT LastName,FirstName FROM Persons The result-set will look like this: LastName
FirstName
Hansen
Ola
Svendson
Tove
Pettersen
Kari
SELECT * Example Now we want to select all the columns from the "Persons" table. We use the following SELECT statement:
SELECT * FROM Persons Tip: The asterisk (*) is a quick way of selecting all columns! The result-set will look like this: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Navigation in a Result-set Most database software systems allow navigation in the result-set with programming functions, like: Move-ToFirst-Record, Get-Record-Content, Move-To-Next-Record, etc. Programming functions like these are not a part of this tutorial. To learn about accessing data with function calls, please visit our ADO tutorial or our PHP tutorial.
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5 SQL SELECT DISTINCT Statement This chapter will explain the SELECT DISTINCT statement.
The SQL SELECT DISTINCT Statement In a table, some of the columns may contain duplicate values. This is not a problem, however, sometimes you will want to list only the different (distinct) values in a table. The DISTINCT keyword can be used to return only distinct (different) values.
SQL SELECT DISTINCT Syntax SELECT DISTINCT column_name(s) FROM table_name
SELECT DISTINCT Example The "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select only the distinct values from the column named "City" from the table above. We use the following SELECT statement:
SELECT DISTINCT City FROM Persons The result-set will look like this: City Sandnes Stavanger
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6 SQL WHERE Clause The WHERE clause is used to filter records.
The WHERE Clause The WHERE clause is used to extract only those records that fulfill a specified criterion.
SQL WHERE Syntax SELECT column_name(s) FROM table_name WHERE column_name operator value
WHERE Clause Example The "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select only the persons living in the city "Sandnes" from the table above. We use the following SELECT statement:
SELECT * FROM Persons WHERE City='Sandnes' The result-set will look like this: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
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Quotes Around Text Fields SQL uses single quotes around text values (most database systems will also accept double quotes). Although, numeric values should not be enclosed in quotes. For text values:
This is correct: SELECT * FROM Persons WHERE FirstName='Tove' This is wrong: SELECT * FROM Persons WHERE FirstName=Tove For numeric values:
This is correct: SELECT * FROM Persons WHERE Year=1965 This is wrong: SELECT * FROM Persons WHERE Year='1965'
Operators Allowed in the WHERE Clause With the WHERE clause, the following operators can be used: Operator
Description
=
Equal
Not equal
>
Greater than
<
Less than
>=
Greater than or equal
(SELECT AVG(OrderPrice) FROM Orders) The result-set will look like this: Customer Hansen Nilsen Jensen
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45 SQL COUNT() Function The COUNT() function returns the number of rows that matches a specified criteria.
SQL COUNT(column_name) Syntax The COUNT(column_name) function returns the number of values (NULL values will not be counted) of the specified column:
SELECT COUNT(column_name) FROM table_name
SQL COUNT(*) Syntax The COUNT(*) function returns the number of records in a table:
SELECT COUNT(*) FROM table_name
SQL COUNT(DISTINCT column_name) Syntax The COUNT(DISTINCT column_name) function returns the number of distinct values of the specified column:
SELECT COUNT(DISTINCT column_name) FROM table_name Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but not with Microsoft Access.
SQL COUNT(column_name) Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to count the number of orders from "Customer Nilsen". We use the following SQL statement:
SELECT COUNT(Customer) AS CustomerNilsen FROM Orders WHERE Customer='Nilsen'
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The result of the SQL statement above will be 2, because the customer Nilsen has made 2 orders in total: CustomerNilsen 2
SQL COUNT(*) Example If we omit the WHERE clause, like this:
SELECT COUNT(*) AS NumberOfOrders FROM Orders The result-set will look like this: NumberOfOrders 6 which is the total number of rows in the table.
SQL COUNT(DISTINCT column_name) Example Now we want to count the number of unique customers in the "Orders" table. We use the following SQL statement:
SELECT COUNT(DISTINCT Customer) AS NumberOfCustomers FROM Orders The result-set will look like this: NumberOfCustomers 3 which is the number of unique customers (Hansen, Nilsen, and Jensen) in the "Orders" table.
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46 SQL FIRST() Function The FIRST() Function The FIRST() function returns the first value of the selected column.
SQL FIRST() Syntax SELECT FIRST(column_name) FROM table_name
SQL FIRST() Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the first value of the "OrderPrice" column. We use the following SQL statement:
SELECT FIRST(OrderPrice) AS FirstOrderPrice FROM Orders Tip: Workaround if FIRST() function is not supported:
SELECT OrderPrice FROM Orders ORDER BY O_Id LIMIT 1 The result-set will look like this: FirstOrderPrice 1000
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47 SQL LAST() Function The LAST() Function The LAST() function returns the last value of the selected column.
SQL LAST() Syntax SELECT LAST(column_name) FROM table_name
SQL LAST() Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the last value of the "OrderPrice" column. We use the following SQL statement:
SELECT LAST(OrderPrice) AS LastOrderPrice FROM Orders Tip: Workaround if LAST() function is not supported:
SELECT OrderPrice FROM Orders ORDER BY O_Id DESC LIMIT 1 The result-set will look like this: LastOrderPrice 100
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48 SQL MAX() Function The MAX() Function The MAX() function returns the largest value of the selected column.
SQL MAX() Syntax SELECT MAX(column_name) FROM table_name
SQL MAX() Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the largest value of the "OrderPrice" column. We use the following SQL statement:
SELECT MAX(OrderPrice) AS LargestOrderPrice FROM Orders The result-set will look like this: LargestOrderPrice 2000
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49 SQL MIN() Function The MIN() Function The MIN() function returns the smallest value of the selected column.
SQL MIN() Syntax SELECT MIN(column_name) FROM table_name
SQL MIN() Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the smallest value of the "OrderPrice" column. We use the following SQL statement:
SELECT MIN(OrderPrice) AS SmallestOrderPrice FROM Orders The result-set will look like this: SmallestOrderPrice 100
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50 SQL SUM() Function The SUM() Function The SUM() function returns the total sum of a numeric column.
SQL SUM() Syntax SELECT SUM(column_name) FROM table_name
SQL SUM() Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the sum of all "OrderPrice" fields". We use the following SQL statement:
SELECT SUM(OrderPrice) AS OrderTotal FROM Orders The result-set will look like this: OrderTotal 5700
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51 SQL GROUP BY Statement Aggregate functions often need an added GROUP BY statement.
The GROUP BY Statement The GROUP BY statement is used in conjunction with the aggregate functions to group the result-set by one or more columns.
SQL GROUP BY Syntax SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name
SQL GROUP BY Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find the total sum (total order) of each customer. We will have to use the GROUP BY statement to group the customers. We use the following SQL statement:
SELECT Customer,SUM(OrderPrice) FROM Orders GROUP BY Customer The result-set will look like this: Customer
SUM(OrderPrice)
Hansen
2000
Nilsen
1700
Jensen
2000
Nice! Isn't it? :)
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Let's see what happens if we omit the GROUP BY statement:
SELECT Customer,SUM(OrderPrice) FROM Orders The result-set will look like this: Customer
SUM(OrderPrice)
Hansen
5700
Nilsen
5700
Hansen
5700
Hansen
5700
Jensen
5700
Nilsen
5700
The result-set above is not what we wanted. Explanation of why the above SELECT statement cannot be used: The SELECT statement above has two columns specified (Customer and SUM(OrderPrice). The "SUM(OrderPrice)" returns a single value (that is the total sum of the "OrderPrice" column), while "Customer" returns 6 values (one value for each row in the "Orders" table). This will therefore not give us the correct result. However, you have seen that the GROUP BY statement solves this problem.
GROUP BY More Than One Column We can also use the GROUP BY statement on more than one column, like this:
SELECT Customer,OrderDate,SUM(OrderPrice) FROM Orders GROUP BY Customer,OrderDate
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52 SQL HAVING Clause The HAVING Clause The HAVING clause was added to SQL because the WHERE keyword could not be used with aggregate functions.
SQL HAVING Syntax SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value
SQL HAVING Example We have the following "Orders" table: O_Id
OrderDate
OrderPrice
Customer
1
2008/11/12
1000
Hansen
2
2008/10/23
1600
Nilsen
3
2008/09/02
700
Hansen
4
2008/09/03
300
Hansen
5
2008/08/30
2000
Jensen
6
2008/10/04
100
Nilsen
Now we want to find if any of the customers have a total order of less than 2000. We use the following SQL statement:
SELECT Customer,SUM(OrderPrice) FROM Orders GROUP BY Customer HAVING SUM(OrderPrice)1500
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The result-set will look like this: Customer
SUM(OrderPrice)
Hansen
2000
Jensen
2000
53 SQL UCASE() Function The UCASE() Function The UCASE() function converts the value of a field to uppercase.
SQL UCASE() Syntax SELECT UCASE(column_name) FROM table_name
Syntax for SQL Server SELECT UPPER(column_name) FROM table_name
SQL UCASE() Example We have the following "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select the content of the "LastName" and "FirstName" columns above, and convert the "LastName" column to uppercase. We use the following SELECT statement:
SELECT UCASE(LastName) as LastName,FirstName FROM Persons The result-set will look like this: LastName
FirstName
HANSEN
Ola
SVENDSON
Tove
PETTERSEN
Kari
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54 SQL LCASE() Function The LCASE() Function The LCASE() function converts the value of a field to lowercase.
SQL LCASE() Syntax SELECT LCASE(column_name) FROM table_name
Syntax for SQL Server SELECT LOWER(column_name) FROM table_name
SQL LCASE() Example We have the following "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select the content of the "LastName" and "FirstName" columns above, and convert the "LastName" column to lowercase. We use the following SELECT statement:
SELECT LCASE(LastName) as LastName,FirstName FROM Persons The result-set will look like this: LastName
FirstName
hansen
Ola
svendson
Tove
pettersen
Kari
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55 SQL MID() Function The MID() Function The MID() function is used to extract characters from a text field.
SQL MID() Syntax SELECT MID(column_name,start[,length]) FROM table_name Parameter
Description
column_name
Required. The field to extract characters from
start
Required. Specifies the starting position (starts at 1)
length
Optional. The number of characters to return. If omitted, the MID() function returns the rest of the text
SQL MID() Example We have the following "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to extract the first four characters of the "City" column above. We use the following SELECT statement:
SELECT MID(City,1,4) as SmallCity FROM Persons The result-set will look like this: SmallCity Sand Sand Stav
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56 SQL LEN() Function The LEN() Function The LEN() function returns the length of the value in a text field.
SQL LEN() Syntax SELECT LEN(column_name) FROM table_name
SQL LEN() Example We have the following "Persons" table: P_Id
LastName
FirstName
Address
City
1
Hansen
Ola
Timoteivn 10
Sandnes
2
Svendson
Tove
Borgvn 23
Sandnes
3
Pettersen
Kari
Storgt 20
Stavanger
Now we want to select the length of the values in the "Address" column above. We use the following SELECT statement:
SELECT LEN(Address) as LengthOfAddress FROM Persons The result-set will look like this: LengthOfAddress 12 9 9
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57 SQL ROUND() Function The ROUND() Function The ROUND() function is used to round a numeric field to the number of decimals specified.
SQL ROUND() Syntax SELECT ROUND(column_name,decimals) FROM table_name Parameter
Description
column_name
Required. The field to round.
decimals
Required. Specifies the number of decimals to be returned.
SQL ROUND() Example We have the following "Products" table: Prod_Id
ProductName
Unit
UnitPrice
1
Jarlsberg
1000 g
10.45
2
Mascarpone
1000 g
32.56
3
Gorgonzola
1000 g
15.67
Now we want to display the product name and the price rounded to the nearest integer. We use the following SELECT statement:
SELECT ProductName, ROUND(UnitPrice,0) as UnitPrice FROM Products The result-set will look like this: ProductName
UnitPrice
Jarlsberg
10
Mascarpone
33
Gorgonzola
16
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58 SQL NOW() Function The NOW() Function The NOW() function returns the current system date and time.
SQL NOW() Syntax SELECT NOW() FROM table_name
SQL NOW() Example We have the following "Products" table: Prod_Id
ProductName
Unit
UnitPrice
1
Jarlsberg
1000 g
10.45
2
Mascarpone
1000 g
32.56
3
Gorgonzola
1000 g
15.67
Now we want to display the products and prices per today's date. We use the following SELECT statement:
SELECT ProductName, UnitPrice, Now() as PerDate FROM Products The result-set will look like this: ProductName
UnitPrice
PerDate
Jarlsberg
10.45
10/7/2008 11:25:02 AM
Mascarpone
32.56
10/7/2008 11:25:02 AM
Gorgonzola
15.67
10/7/2008 11:25:02 AM
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59 SQL FORMAT() Function The FORMAT() Function The FORMAT() function is used to format how a field is to be displayed.
SQL FORMAT() Syntax SELECT FORMAT(column_name,format) FROM table_name Parameter
Description
column_name
Required. The field to be formatted.
format
Required. Specifies the format.
SQL FORMAT() Example We have the following "Products" table: Prod_Id
ProductName
Unit
UnitPrice
1
Jarlsberg
1000 g
10.45
2
Mascarpone
1000 g
32.56
3
Gorgonzola
1000 g
15.67
Now we want to display the products and prices per today's date (with today's date displayed in the following format "YYYY-MM-DD"). We use the following SELECT statement:
SELECT ProductName, UnitPrice, FORMAT(Now(),'YYYY-MM-DD') as PerDate FROM Products The result-set will look like this: ProductName
UnitPrice
PerDate
Jarlsberg
10.45
2008-10-07
Mascarpone
32.56
2008-10-07
Gorgonzola
15.67
2008-10-07
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60 SQL Quick Reference From W3Schools SQL Statement
Syntax
AND / OR
SELECT column_name(s) FROM table_name WHERE condition AND|OR condition
ALTER TABLE
ALTER TABLE table_name ADD column_name datatype or ALTER TABLE table_name DROP COLUMN column_name
AS (alias)
SELECT column_name AS column_alias FROM table_name or SELECT column_name FROM table_name AS table_alias
BETWEEN
SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2
CREATE DATABASE
CREATE DATABASE database_name
CREATE TABLE
CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name2 data_type, ... )
CREATE INDEX
CREATE INDEX index_name ON table_name (column_name) or CREATE UNIQUE INDEX index_name ON table_name (column_name)
CREATE VIEW
CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition
DELETE
DELETE FROM table_name WHERE some_column=some_value or DELETE FROM table_name (Note: Deletes the entire table!!) DELETE * FROM table_name (Note: Deletes the entire table!!)
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DROP DATABASE
DROP DATABASE database_name
DROP INDEX
DROP INDEX table_name.index_name (SQL Server) DROP INDEX index_name ON table_name (MS Access) DROP INDEX index_name (DB2/Oracle) ALTER TABLE table_name DROP INDEX index_name (MySQL)
DROP TABLE
DROP TABLE table_name
GROUP BY
SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name
HAVING
SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value
IN
SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,..)
INSERT INTO
INSERT INTO table_name VALUES (value1, value2, value3,....) or INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,....)
INNER JOIN
SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LEFT JOIN
SELECT column_name(s) FROM table_name1 LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
RIGHT JOIN
SELECT column_name(s) FROM table_name1 RIGHT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
FULL JOIN
SELECT column_name(s) FROM table_name1 FULL JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LIKE
SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern
ORDER BY
SELECT column_name(s) FROM table_name ORDER BY column_name [ASC|DESC]
SELECT
SELECT column_name(s) FROM table_name
SELECT *
SELECT * FROM table_name
SELECT DISTINCT
SELECT DISTINCT column_name(s) FROM table_name
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SELECT INTO
SELECT * INTO new_table_name [IN externaldatabase] FROM old_table_name or SELECT column_name(s) INTO new_table_name [IN externaldatabase] FROM old_table_name
SELECT TOP
SELECT TOP number|percent column_name(s) FROM table_name
TRUNCATE TABLE
TRUNCATE TABLE table_name
UNION
SELECT column_name(s) FROM table_name1 UNION SELECT column_name(s) FROM table_name2
UNION ALL
SELECT column_name(s) FROM table_name1 UNION ALL SELECT column_name(s) FROM table_name2
UPDATE
UPDATE table_name SET column1=value, column2=value,... WHERE some_column=some_value
WHERE
SELECT column_name(s) FROM table_name WHERE column_name operator value
Source : http://www.w3schools.com/sql/sql_quickref.asp
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61 SQL Hosting SQL Hosting If you want your web site to be able to store and display data from a database, your web server should have access to a database system that uses the SQL language. If your web server will be hosted by an Internet Service Provider (ISP), you will have to look for SQL hosting plans. The most common SQL hosting databases are MySQL, MS SQL Server, and MS Access. You can have SQL databases on both Windows and Linux/UNIX operating systems. Below is an overview of which database system that runs on which OS. MS SQL Server Runs only on Windows OS. MySQL Runs on both Windows and Linux/UNIX operating systems. MS Access (recommended only for small websites) Runs only on Windows OS. To learn more about web hosting, please visit our Hosting tutorial.
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62 You Have Learned SQL, Now What? SQL Summary This SQL tutorial has taught you the standard computer language for accessing and manipulating database systems. You have learned how to execute queries, retrieve data, insert new records, delete records and update records in a database with SQL. You have also learned how to create databases, tables, and indexes with SQL, and how to drop them. You have learned the most important aggregate functions in SQL. You now know that SQL is the standard language that works with all the well-known database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and MS Access.
Now You Know SQL, What's Next? Our recommendation is to learn about ADO or PHP MySQL. If you want to learn more about ADO, please visit our ADO tutorial. If you want to learn more about MySQL, please visit our PHP tutorial.
63 SQL Quiz You can test your SQL skills with W3Schools' Quiz.
The Test The test contains 20 questions and there is no time limit. The test is not official, it's just a nice way to see how much you know, or don't know, about SQL.
Your Score Will be Counted You will get 1 point for each correct answer. At the end of the Quiz, your total score will be displayed. Maximum score is 20 points. Good luck! Start the SQL Quiz
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