MySql IFNULL usage instructions, mysqlifnull

MySql IFNULL usage instructions, mysqlifnull

IFNULL (expr1, expr2)

If expr1 is not NULL, IFNULL () returns expr1; otherwise, it returns expr2. IFNULL () returns a number or string value

For example, the current student table (tbl_student) and score table (score) are used to query all the fields in the student table and the English score (engish_score) of the student table. The SQL statement is as follows:

Select stu. *, IFNULL (score. engish_score, 0) from tbl_student stu, tbl_score score where 1 = 1 and stu. stu_id = score. stu_id

In the preceding SQL statement, if the score table contains a value for engish_score, IFNULL (score. engish_score, 0) indicates engish_score. Otherwise, 0 is displayed.