How to use IFNULL function to determine empty string in MySQL?

You can use the IFNULL function in MySQL to evaluate empty strings. The syntax of the IFNULL function is as follows:

IFNULL(expr1, expr2)

expr1 is the value to be evaluated, while expr2 is the replacement value when expr1 is NULL.

To check for empty strings, you can consider an empty string as expr1 and its replacement value as expr2. For example:

SELECT IFNULL('', '空字符串') AS result;

This will return an empty string, indicating that the empty string is considered empty and is replaced with an empty string.

If you want to check if a field’s value is an empty string, you can use that field as expr1. For example:

SELECT IFNULL(column_name, '字段为空') AS result
FROM table_name;

This will return an empty field, indicating that the field is blank and replaced with an empty field.