许多条件取决于 WHERE 子句中的 IF 子句

Question

How can I implement a WHERE clause that depends on one @value condition, like that pseudocode below:

Select * from table
WHERE
IF(@value is not null) 
    Id > 10 and Name = 'example' and Address is not null and ... etc
ELSE 
    Email is not null

Answer 1

As you've seen you can't use an if like that, but you can create the desired behavior using the and and or logical operators:

SELECT *
FROM   table
WHERE  (@value IS NOT NULL AND 
        id > 10 AND 
        name = 'example' AND 
        address IS NOT NULL AND -- etc...) OR
       (@value IS NULL AND email IS NOT NULL)

Answer 2

You want return records with email is not null only when @value is null .
You need to specify "precondition" for both "branches" of "if.. else" in your example.

SELECT *
FROM Table
WHERE (@value IS NOT NULL AND Id > 10 AND ....)
    OR (@value IS NULL AND Email IS NOT NULL)