How to convert function in Mysql numeric type

Mysql numeric type conversion function method: 1. Use the function concat to convert Int to varchar; 2. Use [cast (a as signed) a] to convert varchar to Int.

More related free learning recommendations: mysql tutorial(video)

Mysql numeric type conversion function method:

1. Convert Int to varchar often use the concat function, such as concat(8,'0') to get the string '80'

and MENU_NAME LIKE CONCAT(CONCAT('%', #{pd.keywords}),'%')

2. Convert varchar to Int using cast(a as signed) a is a string of varchar type

Summary: Type conversion is the same as SQL Server, but the type parameters are a little different: CAST(xxx AS type ), CONVERT(xxx, type)

Available types

• Binary, with the effect of binary prefix: BINARY

• Character type, can take parameters: CHAR()

• Date: DATE

• Time: TIME

• Date time type: DATETIME

• Floating point: DECIMAL

• Integer: SIGNED

• Unsigned integer: UNSIGNED

SELECT * from  sys_menu  where  PARENT_ID='0' ORDER BY   cast(MENU_NO as signed)

When MENU_NO is a letter or Chinese character, the converted number is 0.

3. When we need to frequently modify the sorting of a user list, we need to use the situation where the serial number is a decimal. Because if it is an integer, then after adjusting the first one, all subsequent numbers must be adjusted. So we use decimals to sort.

For example 3 3.1 3.2 3.201 3.9 4

In sql we need

order by u.NUMBER+0
NUMBER 的mysql数据库类型为varchar。

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