Detailed explanation of the usage of the ESCAPE keyword in MySQL

MySQL escape

Escape means the original semantics of the escape character. The purpose of an escape character is to start a character sequence so that the character sequence starting with the escape character has different semantics than when the character sequence appears alone.

In MySQL, the escape character starts with "\". The escape characters commonly used in programming are all valid in MySQL and will not be described or discussed here. Here, the role of the ESCAPE keyword is mainly explained through "%" and "_".

%: Matches any number of characters.

_: Matches a single character.

If we want to match "%" or "_", we must use "\" to escape, as follows:

### Query users whose names contain the character "明"> SELECT * FROM user WHERE name LIKE CONCAT("%", "明", "%")
 
### Query users whose names contain the % character> SELECT * FROM user WHERE name LIKE CONCAT("%", "\%", "%")

Usage of ESCAPE

The main function of the ESCAPE keyword is to specify a character to replace the "\".

### Query users whose names contain the "%" character> SELECT * FROM user WHERE name LIKE CONCAT("%", "$%", "%") ESCAPE "$"
 
### Query users whose names contain the "_" character> SELECT * FROM user WHERE name LIKE CONCAT("%", "a_", "%") ESCAPE "a"

It should be noted that all characters indicated by ESCAPE in the query conditions will replace the function of "\".

### Assume there are two users named %a and %_> SELECT * FROM user WHERE name LIKE "a%_" ESCAPE "a" ### %a %_ 
> SELECT * FROM user WHERE name LIKE "a%a" ESCAPE "a" ### %a 
> SELECT * FROM user WHERE name LIKE "a%a_" ESCAPE "a" ### %_

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