SQL Quick Reference

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SQL Quick Reference from W3Schools. Print it, and fold it in your pocket.

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SQL Syntax

Statement	Syntax
AND / OR	SELECT column_name(s) FROM table_name WHERE condition AND|OR condition
ALTER TABLE (add column)	ALTER TABLE table_name ADD column_name datatype
ALTER TABLE (drop column)	ALTER TABLE table_name DROP COLUMN column_name
AS (alias for column)	SELECT column_name AS column_alias FROM table_name
AS (alias for table)	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 INDEX	CREATE INDEX index_name ON table_name (column_name)
CREATE TABLE	CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, ....... )
CREATE UNIQUE INDEX	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 FROM	DELETE FROM table_name (Note: Deletes the entire table!!) or DELETE FROM table_name WHERE condition
DROP DATABASE	DROP DATABASE database_name
DROP INDEX	DROP INDEX table_name.index_name
DROP TABLE	DROP TABLE table_name
GROUP BY	SELECT column_name1,SUM(column_name2) FROM table_name GROUP BY column_name1
HAVING	SELECT column_name1,SUM(column_name2) FROM table_name GROUP BY column_name1 HAVING SUM(column_name2) condition value
IN	SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,..)
INSERT INTO	INSERT INTO table_name VALUES (value1, value2,....) or INSERT INTO table_name (column_name1, column_name2,...) VALUES (value1, value2,....)
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
SELECT INTO (used to create backup copies of tables)	SELECT * INTO new_table_name FROM original_table_name or SELECT column_name(s) INTO new_table_name FROM original_table_name
TRUNCATE TABLE (deletes only the data inside the table)	TRUNCATE TABLE table_name
UPDATE	UPDATE table_name SET column_name=new_value [, column_name=new_value] WHERE column_name=some_value
WHERE	SELECT column_name(s) FROM table_name WHERE condition

Source : http://www.w3schools.com/sql/sql_quickref.asp

SQL CREATE VIEW Statement

A view is a virtual table based on the result-set of a SELECT statement.

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What is a View?

In SQL, a VIEW is a virtual table based on the result-set of a SELECT statement.

A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database. You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the data were coming from a single table.

Note: The database design and structure will NOT be affected by the functions, where, or join statements in a view.

Syntax

CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition

Note: The database does not store the view data! The database engine recreates the data, using the view's SELECT statement, every time a user queries a view.

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Using Views

A view could be used from inside a query, a stored procedure, or from inside another view. By adding functions, joins, etc., to a view, it allows you to present exactly the data you want to the user.

The sample database Northwind has some views installed by default. The view "Current Product List" lists all active products (products that are not discontinued) from the Products table. The view is created with the following SQL:

CREATE VIEW [Current Product List] AS SELECT ProductID,ProductName FROM Products WHERE Discontinued=No

We can query the view above as follows:

SELECT * FROM [Current Product List]

Another view from the Northwind sample database selects every product in the Products table that has a unit price that is higher than the average unit price:

CREATE VIEW [Products Above Average Price] AS SELECT ProductName,UnitPrice FROM Products WHERE UnitPrice>(SELECT AVG(UnitPrice) FROM Products)

We can query the view above as follows:

SELECT * FROM [Products Above Average Price]

Another example view from the Northwind database calculates the total sale for each category in 1997. Note that this view selects its data from another view called "Product Sales for 1997":

CREATE VIEW [Category Sales For 1997] AS SELECT DISTINCT CategoryName,Sum(ProductSales) AS CategorySales FROM [Product Sales for 1997] GROUP BY CategoryName

We can query the view above as follows:

SELECT * FROM [Category Sales For 1997]

We can also add a condition to the query. Now we want to see the total sale only for the category "Beverages":

SELECT * FROM [Category Sales For 1997] WHERE CategoryName='Beverages'

SQL SELECT INTO Statement

The SELECT INTO Statement

The SELECT INTO statement is most often used to create backup copies of tables or for archiving records.

Syntax

SELECT column_name(s) INTO newtable [IN externaldatabase] FROM source

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Make a Backup Copy

The following example makes a backup copy of the "Persons" table:

SELECT * INTO Persons_backup FROM Persons

The IN clause can be used to copy tables into another database:

SELECT Persons.* INTO Persons IN 'Backup.mdb' FROM Persons

If you only want to copy a few fields, you can do so by listing them after the SELECT statement:

SELECT LastName,FirstName INTO Persons_backup FROM Persons

You can also add a WHERE clause. The following example creates a "Persons_backup" table with two columns (FirstName and LastName) by extracting the persons who lives in "Sandnes" from the "Persons" table:

SELECT LastName,Firstname INTO Persons_backup FROM Persons WHERE City='Sandnes'

Selecting data from more than one table is also possible. The following example creates a new table "Empl_Ord_backup" that contains data from the two tables Employees and Orders:

SELECT Employees.Name,Orders.Product INTO Empl_Ord_backup FROM Employees INNER JOIN Orders ON Employees.Employee_ID=Orders.Employee_ID

SQL DELETE Statement

The DELETE Statement

The DELETE statement is used to delete rows in a table.

Syntax

DELETE FROM table_name WHERE column_name = some_value

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Person:

LastName	FirstName	Address	City
Nilsen	Fred	Kirkegt 56	Stavanger
Rasmussen	Nina	Stien 12	Stavanger

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Delete a Row

"Nina Rasmussen" is going to be deleted:

DELETE FROM Person WHERE LastName = 'Rasmussen'

Result

LastName	FirstName	Address	City
Nilsen	Fred	Kirkegt 56	Stavanger

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Delete All Rows

It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

DELETE FROM table_name or DELETE * FROM table_name

SQL UPDATE Statement

The Update Statement

The UPDATE statement is used to modify the data in a table.

Syntax

UPDATE table_name SET column_name = new_value WHERE column_name = some_value

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Person:

LastName	FirstName	Address	City
Nilsen	Fred	Kirkegt 56	Stavanger
Rasmussen		Storgt 67

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Update one Column in a Row

We want to add a first name to the person with a last name of "Rasmussen":

UPDATE Person SET FirstName = 'Nina' WHERE LastName = 'Rasmussen'

Result:

LastName	FirstName	Address	City
Nilsen	Fred	Kirkegt 56	Stavanger
Rasmussen	Nina	Storgt 67

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Update several Columns in a Row

We want to change the address and add the name of the city:

UPDATE Person SET Address = 'Stien 12', City = 'Stavanger' WHERE LastName = 'Rasmussen'

Result:

LastName	FirstName	Address	City
Nilsen	Fred	Kirkegt 56	Stavanger
Rasmussen	Nina	Stien 12	Stavanger

SQL INSERT INTO Statement

The INSERT INTO Statement

The INSERT INTO statement is used to insert new rows into a table.

Syntax

INSERT INTO table_name VALUES (value1, value2,....)

You can also specify the columns for which you want to insert data:

INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,....)

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Insert a New Row

This "Persons" table:

LastName	FirstName	Address	City
Pettersen	Kari	Storgt 20	Stavanger

And this SQL statement:

INSERT INTO Persons VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes')

Will give this result:

LastName	FirstName	Address	City
Pettersen	Kari	Storgt 20	Stavanger
Hetland	Camilla	Hagabakka 24	Sandnes

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Insert Data in Specified Columns

This "Persons" table:

LastName	FirstName	Address	City
Pettersen	Kari	Storgt 20	Stavanger
Hetland	Camilla	Hagabakka 24	Sandnes

And This SQL statement:

INSERT INTO Persons (LastName, Address) VALUES ('Rasmussen', 'Storgt 67')

Will give this result:

LastName	FirstName	Address	City
Pettersen	Kari	Storgt 20	Stavanger
Hetland	Camilla	Hagabakka 24	Sandnes
Rasmussen		Storgt 67

The SQL SELECT Statement

The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result-set).

Syntax

SELECT column_name(s) FROM table_name

Note: SQL statements are not case sensitive. SELECT is the same as select.

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SQL SELECT Example

To select the content of columns named "LastName" and "FirstName", from the database table called "Persons", use a SELECT statement like this:

SELECT LastName,FirstName FROM Persons

The database table "Persons":

LastName	FirstName	Address	City
Hansen	Ola	Timoteivn 10	Sandnes
Svendson	Tove	Borgvn 23	Sandnes
Pettersen	Kari	Storgt 20	Stavanger

The result

LastName	FirstName
Hansen	Ola
Svendson	Tove
Pettersen	Kari

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Select All Columns

To select all columns from the "Persons" table, use a * symbol instead of column names, like this:

SELECT * FROM Persons

Result

LastName	FirstName	Address	City
Hansen	Ola	Timoteivn 10	Sandnes
Svendson	Tove	Borgvn 23	Sandnes
Pettersen	Kari	Storgt 20	Stavanger

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The Result Set

The result from a SQL query is stored in a result-set. Most database software systems allow navigation of the result set with programming functions, like: Move-To-First-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.

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Semicolon after SQL Statements?

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.

Some SQL tutorials end each SQL statement with a semicolon. Is this necessary? 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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The SELECT DISTINCT Statement

The DISTINCT keyword is used to return only distinct (different) values.

The SELECT statement returns information from table columns. But what if we only want to select distinct elements?

With SQL, all we need to do is to add a DISTINCT keyword to the SELECT statement:

Syntax

SELECT DISTINCT column_name(s) FROM table_name

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Using the DISTINCT keyword

To select ALL values from the column named "Company" we use a SELECT statement like this:

SELECT Company FROM Orders

"Orders" table

Company	OrderNumber
Sega	3412
W3Schools	2312
Trio	4678
W3Schools	6798

Result

Company
Sega
W3Schools
Trio
W3Schools

Note that "W3Schools" is listed twice in the result-set.

To select only DIFFERENT values from the column named "Company" we use a SELECT DISTINCT statement like this:

SELECT DISTINCT Company FROM Orders

Result:

Company
Sega
W3Schools
Trio

Now "W3Schools" is listed only once in the result-set.