SQL不为空，作为CASE语句中的值

Question

I have a scenario where I want to choose non null values if B is equal to 61, I can't seem to find the correct syntax for this.

A          |        B
value1     |        61
value2     |        0 
NULL       |        61


WHERE A = CASE 
    WHEN B = 61
        THEN IS NOT NULL
    END

I want to select only the row with A=value1

Answer 1

为什么不直接前进呢？

WHERE (B=61) AND (A IS NOT NULL)

Answer 2

You can have this like:

//thats really straight forward:
WHERE (A IS NOT NULL AND B=61)

or their is another way of picking you nose :)

WHERE
IF(A IS NOT NULL AND B=61,1,0) //add other conditions as you like

Answer 3

In many situations it isn't necessary to use case expressions or IF() in a where clause, conventionally it is handled by combining conditions in parentheses.

WHERE ( B = 61 AND A IS NOT NULL )

Here both conditions must be true for the combined condition to be true