The WHERE statement for SQL

Source: Internet
Author: User
Tags numeric value

WHERE clause

To conditionally select data from a table, you can add a WHERE clause to the SELECT statement.

Grammar

SELECT column name from table name WHERE column operator value

The following operators can be used in the WHERE clause:

operator Description
= Equals
<> Not equal to
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
Between Within a range
Like Search for a pattern

Notes: In some versions of SQL, the operator <> can be written as! =.

Using the WHERE clause

If you want to select only people who live in the city "Beijing", we need to add a WHERE clause to the SELECT statement:

WHERE City=‘Beijing‘
"Persons" table City Year
LastName FirstName Address
Adams John Oxford Street London 1970
Bush George Fifth Avenue New York 1975
Carter Thomas Changan Street Beijing 1980
Gates Bill Xuanwumen 10 Beijing 1985
Results: City Year
LastName FirstName Address
Carter Thomas Changan Street Beijing 1980
Gates Bill Xuanwumen 10 Beijing 1985

Use of quotation marks

Note that we use single quotes around the condition values in the example.

SQL uses single quotation marks to wrap text values (most database systems also accept double quotes). If it is a numeric value , do not use quotation marks.

Text value:
FirstName=‘Bush‘FirstName=Bush
Numerical:
Year>1965Year>‘1965‘

The WHERE statement for SQL

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