SQL WHERE - SQL Getting Started Tutorial Manual

SQL WHERE

Collection 127

update time 2016-10-15

SQL SELECT DISTINCT

SQL AND & OR

The WHERE clause is used to filter records.

SQL WHERE clause

The WHERE clause is used to extract those records that meet the specified criteria.

SQL WHERE syntax

SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

Demo database

In this tutorial, we will use the php sample database.

The following is the data selected from the "Websites" table:

+----+--------------+--- ------------------------+-------+---------+
| id | name | url --------+-------+---------+
| 1 | Google | https://www.google.cm/ | 1 | USA |
| 2 | Taobao | https://www.taobao.com/ | 13 | CN |
| 3 | php Chinese website | //m.sbmmt.com/ | 4689 | CN |
| 4 | Weibo | http://weibo.com/ | 20 | CN |
| 5 | Facebook | https://www.facebook.com/ | 3 | USA |
+--- -+-------------+--------------------------+----- --+---------+

WHERE clause example

The following SQL statement selects the country "CN" from the "Websites" table "All websites:

Example

SELECT * FROM Websites WHERE country='CN';

Execution output result:

Text fields vs. numeric fields

SQL uses single quotes to surround text values (most database systems also accept double quotes quotation marks).

In the previous example, single quotes were used in the 'CN' text field.

If it is a numeric field, please do not use quotation marks.

Example

SELECT * FROM Websites WHERE id=1;

Execution output result:

##Operators in the WHERE clause

The following operators can be used in the WHERE clause:

OperatorDescription= is equal to <> is not equal to. > is greater than < is less than >= is greater than or equal to <=Less than or equal toBETWEENWithin a certain rangeLIKESearch for a patternINSpecify multiple possible values for a column