Quick comparison of some columns in the MySQL field _ MySQL

Quickly tune certain columns in the MySQL field

Q: The table t has a field called c. Now I want to check the 10th and 11th columns in column c. What should I do?

Answer: Use the following method. However, this example only applies to ascii characters. you can find another method for Chinese characters or other characters.

Mysql> set @ pos1 = 10;
Mysql> set @ pos2 = 11;
Mysql> UPDATEtSETc = CONCAT (
LEFT (c, @ pos1-1), -- values earlier than 10th columns
SUBSTR (c, @ pos2, 1), -- Value of column 11th
SUBSTR (c, @ pos1 + 1, @ pos2-@ pos1-1), -- value between 10th and 11th columns
SUBSTR (c, @ pos1, 1), -- column 10th
RIGHT (c, LENGTH (c)-@ pos2); -- value after column 11th

In fact, it is very simple :)