1. SQL Tutorial
w3schools

2. Intro
Intro

3. Sql intro
SQL is a standard language for accessing and manipulating databases.

4. Sql intro SQL stands for Structured Query Language
What is SQL?
SQL stands for Structured Query Language
SQL lets you access and manipulate databases
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987

5. Sql intro SQL can execute queries against a database
What Can SQL do?
SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

6. Sql intro
SQL is a Standard - BUT....
Although SQL is an ANSI/ISO standard, there are 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!

7. Sql intro
Using SQL in Your Web Site
To build a web site that shows data from a database, you will need:
An RDBMS database program (i.e. MS Access, SQL Server, MySQL)
To use a server-side scripting language, like PHP or ASP
To use SQL to get the data you want
To use HTML / CSS to style the page

8. Sql intro
RDBMS
RDBMS stands for Relational Database Management System. RDBMS is the basis for SQL, and for all modern database systems such as 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 collection of related data entries and it consists of columns and rows. Look at the "Customers" table: SELECT * FROM Customers; Try it Yourself:

9. Sql intro
RDBMS Continued
Every table is broken up into smaller entities called fields. The fields in the Customers table consist of CustomerID, CustomerName, ContactName, Address, City, PostalCode and Country. A field is a column in a table that is designed to maintain specific information about every record in the table. A record, also called a row, is each individual entry that exists in a table. For example, there are 91 records in the above Customers table. A record is a horizontal entity in a table. A column is a vertical entity in a table that contains all information associated with a specific field in a table.

10. Syntax
Syntax

11. 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. In this tutorial we will use the well-known Northwind sample database (included in MS Access and MS SQL Server).

12. Sql syntax Database Tables Continued
Below is a selection from the "Customers" table: The table above contains five records (one for each customer) and seven columns (CustomerID, CustomerName, ContactName, Address, City, PostalCode, and Country).
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

13. Sql syntax
SQL Statements
Most of the actions you need to perform on a database are done with SQL statements. The following SQL statement selects all the records in the "Customers" table: SELECT * FROM Customers; Try it Yourself: In this tutorial we will teach you all about the different SQL statements.

14. Sql syntax
Keep in Mind That...
SQL keywords are NOT case sensitive: select is the same as SELECT
In this tutorial we will write all SQL keywords in upper-case.

15. Sql syntax
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. In this tutorial, we will use semicolon at the end of each SQL statement.

16. Sql syntax SELECT - extracts data from a database
Some of The Most Important SQL Commands
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
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

17. SELECT
Select

18. Sql select
The SQL SELECT Statement
The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set. SELECT Syntax SELECT column1, column2, ... FROM table_name; Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax: SELECT * FROM table_name;

19. Sql select
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

20. Sql select
SELECT Column Example
The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table: SELECT CustomerName, City FROM Customers; Try it Yourself:

21. Sql select
Test Yourself With Exercises
Start the Exercise

22. SELECT DISTINCT
Select Distinct

23. Sql select Distinct
The SQL SELECT DISTINCT Statement
The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values. SELECT DISTINCT Syntax SELECT DISTINCT column1, column2, ... FROM table_name;

24. Sql select Distinct
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

25. Sql select Distinct
SELECT Example
The following SQL statement selects all (and duplicate) values from the "Country" column in the "Customers" table: SELECT Country FROM Customers; Try it Yourself: Now, let us use the DISTINCT keyword with the above SELECT statement and see the result.

26. Sql select Distinct
SELECT DISTINCT Examples
The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table: SELECT DISTINCT Country FROM Customers; Try it Yourself: The following SQL statement lists the number of different (distinct) customer countries: SELECT COUNT(DISTINCT Country) FROM Customers; Try it Yourself:

27. Sql select Distinct
SELECT DISTINCT Examples Continued
Here is the workaround for MS Access: SELECT Count(*) AS DistinctCountries FROM (SELECT DISTINCT Country FROM Customers); Try it Yourself:
Note: The previous example will not work in Firefox and Microsoft Edge! Because COUNT(DISTINCT column_name) is not supported in Microsoft Access databases. Firefox and Microsoft Edge are using Microsoft Access in our examples.

28. Sql select Distinct
Test Yourself With Exercises
Start the Exercise

29. WHERE
Where

30. Sql where
The SQL WHERE Clause
The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition. WHERE Syntax SELECT column1, column2, ... FROM table_name WHERE condition;
Note: The WHERE clause is not only used in SELECT statement, it is also used in UPDATE, DELETE statement, etc.!

31. Sql where
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

32. Sql where
WHERE Clause Example
The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table: SELECT * FROM Customers WHERE Country='Mexico’; Try it Yourself:

33. Sql where
Text Fields vs. Numeric Fields
SQL requires single quotes around text values (most database systems will also allow double quotes). However, numeric fields should not be enclosed in quotes: SELECT * FROM Customers WHERE CustomerID=1; Try it Yourself:

34. Sql where The following operators can be used in the WHERE clause:
Operators in The WHERE Clause
The following operators can be used in the WHERE clause:
Operator
Description =
Equal
<>
Not equal. Note: In some versions of SQL this operator may be written as !=
>
Greater than
<
Less than
>=
Greater than or equal
<=
Less than or equal
BETWEEN
Between a certain range
LIKE
Search for a pattern IN
To specify multiple possible values for a column

35. Sql where
Test Yourself With Exercises
Start the Exercise

36. AND, Or, Not
And, Or, Not

37. Sql and or not
The SQL AND, OR and NOT Operators
The WHERE clause can be combined with AND, OR, and NOT operators.
The AND and OR operators are used to filter records based on more than one condition:
The AND operator displays a record if all the conditions separated by AND are TRUE.
The OR operator displays a record if any of the conditions separated by OR is TRUE.
The NOT operator displays a record if the condition(s) is NOT TRUE.

38. Sql and or not
The SQL AND, OR and NOT Operators Continued
AND Syntax SELECT column1, column2, ... FROM table_name WHERE condition1 AND condition2 AND condition3 ...; OR Syntax SELECT column1, column2, ... FROM table_name WHERE condition1 OR condition2 OR condition3 ...; NOT Syntax SELECT column1, column2, ... FROM table_name WHERE NOT condition;

39. Sql and or not
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

40. Sql and or not
AND Example
The following SQL statement selects all fields from "Customers" where country is "Germany" AND city is "Berlin": SELECT * FROM Customers WHERE Country='Germany' AND City='Berlin’; Try it Yourself:

41. Sql and or not
OR Example
The following SQL statement selects all fields from "Customers" where city is "Berlin" OR "München": SELECT * FROM Customers WHERE City='Berlin' OR City='München’; Try it Yourself:

42. Sql and or not
NOT Example
The following SQL statement selects all fields from "Customers" where country is NOT "Germany": SELECT * FROM Customers WHERE NOT Country='Germany’; Try it Yourself:

43. Sql and or not
Combining AND, OR and NOT
You can also combine the AND, OR and NOT operators. The following SQL statement selects all fields from "Customers" where country is "Germany" AND city must be "Berlin" OR "München" (use parenthesis to form complex expressions): SELECT * FROM Customers WHERE Country='Germany' AND (City='Berlin' OR City='München’); Try it Yourself: The following SQL statement selects all fields from "Customers" where country is NOT "Germany" and NOT "USA": SELECT * FROM Customers WHERE NOT Country='Germany' AND NOT Country='USA’; Try it Yourself:

44. Sql and or not
Test Yourself With Exercises
Start the Exercise

45. ORDER BY
Order By

46. Sql order by
The SQL ORDER BY Keyword
The ORDER BY keyword is used to sort the result-set in ascending or descending order. The ORDER BY keyword sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword. ORDER BY Syntax SELECT column1, column2, ... FROM table_name ORDER BY column1, column2, ... ASC|DESC;

47. Sql order by
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

48. Sql order by
ORDER BY Example
The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" column: SELECT * FROM Customers ORDER BY Country; Try it Yourself:

49. Sql order by
ORDER BY DESC Example
The following SQL statement selects all customers from the "Customers" table, sorted DESCENDING by the "Country" column: SELECT * FROM Customers ORDER BY Country DESC; Try it Yourself:

50. Sql order by
ORDER BY Several Columns Example
The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" and the "CustomerName" column. This means that it orders by Country, but if some rows have the same Country, it orders them by CustomerName: SELECT * FROM Customers ORDER BY Country, CustomerName; Try it Yourself:

51. Sql order by
ORDER BY Several Columns Example 2
The following SQL statement selects all customers from the "Customers" table, sorted ascending by the "Country" and descending by the "CustomerName" column: SELECT * FROM Customers ORDER BY Country ASC, CustomerName DESC; Try it Yourself:

52. Sql order by
Test Yourself With Exercises
Start the Exercise

53. INSERT INTO
Insert Into

54. Sql Insert into
The SQL INSERT INTO Statement
The INSERT INTO statement is used to insert new records in a table. INSERT INTO Syntax It is possible to write the INSERT INTO statement in two ways. The first way specifies both the column names and the values to be inserted: INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); If you are adding values for all the columns of the table, you do not need to specify the column names in the SQL query. However, make sure the order of the values is in the same order as the columns in the table. The INSERT INTO syntax would be as follows: INSERT INTO table_name VALUES (value1, value2, value3, ...);

55. Sql Insert into
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 89
White Clover Markets
Karl Jablonski
th Ave. S. Suite 3B
Seattle
98128
USA 90
Wilman Kala
Matti Karttunen
Keskuskatu 45
Helsinki
21240
Finland 91
Wolski
Zbyszek
ul. Filtrowa 68
Walla
01-012
Poland

56. Sql Insert into
INSERT INTO Example
The following SQL statement inserts a new record in the "Customers" table: INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country) VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway’); Try it Yourself:

57. Sql Insert into
INSERT INTO Example Continued
The selection from the "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 89
White Clover Markets
Karl Jablonski
th Ave. S. Suite 3B
Seattle
98128
USA 90
Wilman Kala
Matti Karttunen
Keskuskatu 45
Helsinki
21240
Finland 91
Wolski
Zbyszek
ul. Filtrowa 68
Walla
01-012
Poland 92
Cardinal
Tom B. Erichsen
Skagen 21
Stavanger
4006
Norway

58. Sql Insert into INSERT INTO Example Continued
Did you notice that we did not insert any number into the CustomerID field? The CustomerID column is an auto-increment field and will be generated automatically when a new record is inserted into the table.

59. Sql Insert into
Insert Data Only in Specified Columns
It is also possible to only insert data in specific columns. The following SQL statement will insert a new record, but only insert data in the "CustomerName", "City", and "Country" columns (CustomerID will be updated automatically): INSERT INTO Customers (CustomerName, City, Country) VALUES ('Cardinal', 'Stavanger', 'Norway’); Try it Yourself:

60. Sql Insert into
Insert Data Only in Specified Columns Continued
The selection from the "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 89
White Clover Markets
Karl Jablonski
th Ave. S. Suite 3B
Seattle
98128
USA 90
Wilman Kala
Matti Karttunen
Keskuskatu 45
Helsinki
21240
Finland 91
Wolski
Zbyszek
ul. Filtrowa 68
Walla
01-012
Poland 92
Cardinal
null
null 
Stavanger
Norway

61. Sql Insert into
Test Yourself With Exercises
Start the Exercise

62. NULL
Null Values

63. Sql Null values
What is a NULL Value?
A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL value.
Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation!

64. Sql Null values
How to Test for NULL Values?
It is not possible to test for NULL values with comparison operators, such as =, <, or <>. We will have to use the IS NULL and IS NOT NULL operators instead. IS NULL Syntax SELECT column_names FROM table_name WHERE column_name IS NULL; IS NOT NULL Syntax SELECT column_names FROM table_name WHERE column_name IS NOT NULL;

65. Sql Null values
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

66. Tip: Always use IS NULL to look for NULL values.
Sql Null values
The IS NULL Operator
The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field: SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NULL; Try it Yourself:
Tip: Always use IS NULL to look for NULL values.

67. Sql Null values
The IS NOT NULL Operator
The IS NOT NULL operator is used to test for non-empty values (NOT NULL values). The following SQL lists all customers with a value in the "Address" field: SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NOT NULL; Try it Yourself:

68. Sql Null values
Test Yourself With Exercises
Start the Exercise

69. UPDATE
Update

70. Sql update
The SQL UPDATE Statement
The UPDATE statement is used to modify the existing records in a table. UPDATE Syntax UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;
Note: Be careful when updating records in a table! Notice the WHERE clause in the UPDATE statement. The WHERE clause specifies which record(s) that should be updated. If you omit the WHERE clause, all records in the table will be updated!

71. Sql update
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

72. Sql update
UPDATE Table
The following SQL statement updates the first customer (CustomerID = 1) with a new contact person and a new city. UPDATE Customers SET ContactName = 'Alfred Schmidt', City= 'Frankfurt' WHERE CustomerID = 1; Try it Yourself:

73. Sql update
UPDATE Table Continued
The selection from the "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Alfred Schmidt
Obere Str. 57
Frankfurt
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

74. Sql update
UPDATE Multiple Records
It is the WHERE clause that determines how many records that will be updated. The following SQL statement will update the contactname to "Juan" for all records where country is "Mexico": UPDATE Customers SET ContactName='Juan' WHERE Country='Mexico’; Try it Yourself:

75. Sql update
UPDATE Multiple Records Continued
The selection from the "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Alfred Schmidt
Obere Str. 57
Frankfurt
12209
Germany 2
Ana Trujillo Emparedados y helados
Juan
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

76. Sql update
Update Warning!
UPDATE Customers SET ContactName='Juan’; Try it Yourself:
Be careful when updating records. If you omit the WHERE clause, ALL records will be updated!

77. Sql update
Update Warning! Continued
The selection from the "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Juan
Obere Str. 57
Frankfurt
12209
Germany 2
Ana Trujillo Emparedados y helados
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Mataderos 2312
05023 4
Around the Horn
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Berguvsvägen 8
Luleå S
Sweden

78. Sql update
Test Yourself With Exercises
Start the Exercise

79. DELETE
Delete

80. Sql Delete
The SQL DELETE Statement
The DELETE statement is used to delete existing records in a table. DELETE Syntax DELETE FROM table_name WHERE condition;
Note: Be careful when deleting records in a table! Notice the WHERE clause in the DELETE statement. The WHERE clause specifies which record(s) should be deleted. If you omit the WHERE clause, all records in the table will be deleted!

81. Sql Delete
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

82. Sql Delete
SQL DELETE Example
The following SQL statement deletes the customer "Alfreds Futterkiste" from the "Customers" table: DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste’; Try it Yourself:

83. Sql Delete The "Customers" table will now look like this:
SQL DELETE Example Continued
The "Customers" table will now look like this:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 2
Ana Trujillo Emparedados y helados
Ana Trujillo
Avda. de la Constitución 2222
México D.F.
05021
Mexico 3
Antonio Moreno Taquería
Antonio Moreno
Mataderos 2312
05023 4
Around the Horn
Thomas Hardy
120 Hanover Sq.
London
WA1 1DP UK 5
Berglunds snabbköp
Christina Berglund
Berguvsvägen 8
Luleå S
Sweden

84. Sql Delete
Delete All Records
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; The following SQL statement deletes all rows in the "Customers" table, without deleting the table: DELETE FROM Customers; Try it Yourself:

85. Sql Delete
Test Yourself With Exercises
Start the Exercise

86. SELECT TOP
Select Top

87. Sql Select top
The SQL SELECT TOP Clause
The SELECT TOP clause is used to specify the number of records to return. The SELECT TOP clause is useful on large tables with thousands of records. Returning a large number of records can impact on performance. SQL Server / MS Access Syntax: SELECT TOP number|percent column_name(s) FROM table_name WHERE condition;
Note: Not all database systems support the SELECT TOP clause. MySQL supports the LIMIT clause to select a limited number of records, while Oracle uses ROWNUM.

88. Sql Select top
The SQL SELECT TOP Clause Continued
MySQL Syntax: SELECT column_name(s) FROM table_name WHERE condition LIMIT number; Oracle Syntax: SELECT column_name(s) FROM table_name WHERE ROWNUM <= number;

89. Sql Select top
Demo Database
Below is a selection from the "Customers" table in the Northwind sample database:
CustomerID
CustomerName
ContactName
Address
City
PostalCode
Country 1
Alfreds Futterkiste
Maria Anders
Obere Str. 57
Berlin
12209
Germany 2
Ana Trujillo Emparedados y helados
Ana Trujillo
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90. Sql Select top
SQL TOP, LIMIT and ROWNUM Examples
The following SQL statement selects the first three records from the "Customers" table: SELECT TOP 3 * FROM Customers; Try it Yourself: The following SQL statement shows the equivalent example using the LIMIT clause: SELECT * FROM Customers LIMIT 3; Try it Yourself:

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SQL TOP, LIMIT and ROWNUM Examples Continued
The following SQL statement shows the equivalent example using ROWNUM: SELECT * FROM Customers WHERE ROWNUM <= 3;

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SQL TOP PERCENT Example
The following SQL statement selects the first 50% of the records from the "Customers" table: SELECT TOP 50 PERCENT * FROM Customers; Try it Yourself:

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ADD a WHERE CLAUSE
The following SQL statement selects the first three records from the "Customers" table, where the country is "Germany": SELECT TOP 3 * FROM Customers WHERE Country='Germany’; Try it Yourself: The following SQL statement shows the equivalent example using the LIMIT clause: SELECT * FROM Customers WHERE Country='Germany' LIMIT 3; Try it Yourself:

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ADD a WHERE CLAUSE Continued
The following SQL statement shows the equivalent example using ROWNUM: SELECT * FROM Customers WHERE Country='Germany' AND ROWNUM <= 3;