How to convert function of Mysql number type-1024programmer

Mysql number 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 recommendation: mysql tutorial (video)

Mysql number type Method of conversion function:

1. Convert Int to varchar often use the concat function, such as concat(8,'0') to get the string '80& #39;

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

2. Convert varchar to Int and use cast(a as signed) a to varchar type string

Summary: type conversion is the same as SQL Server, The type parameter is a bit different: CAST(xxx AS type), CONVERT(xxx, type)

Available types

Binary, same effect with binary prefix: BINARY
Character type, can take parameters: CHAR()
Date: DATE
Time: TIME
DateTime: DATETIME
Float: 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 want to modify the sorting of a user list frequently, we need It is used when 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
 The mysql database type of NUMBER is varchar.

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