Usage of substring truncation functions in MySql

The commonly used string truncation functions in mysql include substring and SUBSTRING_INDEX. substring is the string whose pos starts to be len. This is a bit like the php string truncation function, let's take a look.

Usage:

SUBSTRING (str, pos, len)
SUBSTRING (str FROM pos FOR len)
SUBSTRING (str, pos)
SUBSTRING (str FROM pos)

Alias SUBSTR

Truncates a string whose str starts from the pos and is len. If the len parameter is not set, all content after the pos is obtained by default.
Note that the index of the string starts from 1.
If pos is a negative number, it is truncated from the end of the string.

1. truncate all pos data

The Code is as follows:	Copy code
Mysql> select substring ('mysql database', 2 ); + ----------- + | Substring ('mysql database', 2) | + ----------- + | Ysql database | + ----------- + 1 row in set

2. truncate the last three characters of the pos

The Code is as follows:	Copy code
Mysql> select substring ('mysql database', 2, 3 ); + ----------- + | Substring ('mysql database', 2, 3) | + ----------- + | Ysq | + ----------- + 1 row in set

3. view some other instances

The Code is as follows:	Copy code
Mysql> select substring ('quadratically ', 5 ); -> 'Ratically' Mysql> select substring ('foobarbar' FROM 4 ); -> 'Barbar' Mysql> select substring ('quadratically ', 5, 6 ); -> 'Ratica' Mysql> select substring ('sakila',-3 ); -> 'Ila' Mysql> select substring ('sakila',-5, 3 ); -> 'Aki' Mysql> select substring ('sakila' FROM-4 FOR 2 ); -> 'Ki'

Now, let's take a look.

Substring_index

Substring_index (str, delim, count)

The Code is as follows:	Copy code
Mysql> SELECT SUBSTRING_INDEX ('www. bKjia. c0m', '.', 2 ); -> 'Www. 111cn' Mysql> SELECT SUBSTRING_INDEX ('www. bKjia. c0m', '.',-2 ); -> 'Bkjia. c0m'