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This article mainly introduces how to convert mysql into varchar, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

Mysql transform varchar method: 1, use cast function conversion; 2, use "select-(- field name) from table name;" way conversion; 3, use "select field name + 0 from table name;" way conversion.

This article operating environment: windows7 system, mysql5.5 version, Dell G3 computer.

MySQL varchar type conversion:

Problem: do the data filtering module, because there is a problem with the original table design, the field in the table is a string, and the filter condition is numeric, so there is no way to compare.

Think about it: you can extract the numbers from the string in the mysql field and compare them

Solution: access to data and find three methods

1. Use the cast function

For example: SELECT CAST (field name AS UNSIGNED) FROM table name

The syntax rule for the cast function is: Cast (the type of field name as conversion), where the type can be:

CHAR [(N)] representative: character type DATE representative: date type DATETIME representative: date type DECIMAL representative: float type SIGNED representative: int TIME representative: time type

For a string at the beginning of a number, the result of conversion to a number is to intercept the previous part of the number, but for a string that cannot intercept a number at the beginning, the result of the conversion is 0, which requires attention.

two。 Use-(- field name)

For example: select-(- field name) from table name

This is more powerful, simple and rough.

3. Use the field name directly + 0

For example: select field name + 0 from table name

This is only used for numbers with all varchar types in the field, and cannot contain Chinese or anything else, otherwise an error will be reported. It is generally recommended to use 1BI 2.

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