Coalesce usage in mysql

In mysql, there are actually a lot of methods and functions that are very useful. This introduction is called coalesce, and spelling is very troublesome, however, the function is to return the first non-null value of the input parameter, for example

Select coalesce (NULL, NULL, 1 );

-- Return 1

Select coalesce (NULL, NULL, 1 );

-- Return 1

If all input parameters are null, null is returned, for example

Select coalesce (NULL, NULL );

-- Return NULL

This parameter is used in the following scenarios: If a field is null by default, you can use this function instead of null, but for example, 0 or other values.

Select coalesce (field_name, 0) as value from table;