Mysql Command Memo

First, MySQL gets the string length method

Length: Are the lengths of the calculated fields a Chinese character is counted as three characters, a number or a letter is counted as a character

Char_length: No matter Chinese characters or numbers or letters are a character

Second, MySQL string length auto-completion

Pre-complement: lpad (field, 4,0)

Update users Set employee_id = Lpad (employee_id,4,0) where id = 1; The first bit of employee_id is less than 4 bits, then 0 to 4 bits are added before

Post-complement: rpad (field, 4,0)

Update users Set employee_id = Rpad (employee_id,4,0) where id = 1;//after filling 4 bits