How to query multiple conditions in MySQL-Mysql Tutorial-php.cn

How to query multiple conditions in MySQL

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Release： 2022-05-26 15:22:35

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Method: 1. Use the "SELECT * FROM table name WHERE condition 1 AND condition 2..." statement to query all conditions in multiple conditions; 2. Use "SELECT * FROM table name WHERE condition 1 OR Condition 2..." statement queries the specified condition among multiple conditions.

How to query multiple conditions in MySQL

The operating environment of this tutorial: windows10 system, mysql8.0.22 version, Dell G3 computer.

How to query multiple conditions in mysql

Conditional query

The SELECT statement can set query conditions through WHERE conditions, and the query results are records that meet the query conditions.

SQL conditional query syntax:

SELECT * FROM <表名> WHERE <条件表达式>;

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Conditional expression:

1, AND , expression that satisfies condition 1 and Condition 2 is met.

The AND operator is a logical operator that combines two or more Boolean expressions, returning true only if both expressions evaluate to true. The AND operator returns false if one of the two expressions evaluates to false.

How to query multiple conditions in MySQL

##2, OR , means that either Condition 1 or Condition 2 is satisfied.

How to query multiple conditions in MySQL

NOT means records that "do not meet the condition".

To combine three or more conditions, you need to use parentheses () to indicate how to perform conditional operations.

Note: If parentheses are not added, the conditional operation is performed according to the priority of NOT, AND, and OR, that is, NOT has the highest priority, followed by AND, and finally OR. Adding parentheses changes the priority.

Extended knowledge:

Basic query

The basic query syntax of SQL: SELECT * FROM ;

The result of the SELECT query is a Two-dimensional table.

The SELECT statement does not actually require a FROM clause. Although SELECT can be used for calculations, it is not the strength of SQL. However, the SELECT statement without a FROM clause has a useful purpose, which is to determine whether the current connection to the database is valid. Many detection tools will execute a SELECT 1; to test the database connection.

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