MySQL Common functions

1.
IsNull (expr): Exper is null, returns TRUE, otherwise false
Ifnull (EXPR1,EXPR2): If EXPR1 is not NULL, the return value of Ifnull () is expr1; Otherwise its return value is EXPR2
Format (X,D): formats X as a number of D decimal places, can format data as integers or floating-point numbers, with rounding function

The 2.concat () function can connect one or more strings
Concat (STR1,STR2,...) returns the string that results from the connection parameter. If any one of the arguments is NULL, the return value is null
Concat_ws (SEPARATOR,STR1,STR2,...) The first parameter is a delimiter for other parameters. The position of the delimiter is placed between the two strings to be concatenated. The delimiter can be a string, or it can be another parameter

3.group_concat () grouping splicing function
Group_concat ([distinct] field to connect [order by Asc/desc sort field] [separator ' delimiter '])

MySQL Common functions