CODEWITHSUNDEEP
mysqloperatorsboolean-expression
Cody
Cody

Reputation: 13

In MySQL, what does the '+' operator do in the context of a boolean expression?

For example:

    IF (SELECT ((new.fieldA IS NULL) + (new.fieldB IS NULL) + (new.fieldC IS NULL)) <> 2)
    THEN
        do some stuff
    END IF;

I am coming to MySQL from PostgreSQL. I came across this syntax (in the select statement) and am having a hard time figuring out what exactly the '+' operators are doing here.

Thanks

Upvotes: 0

Views: 16

Answers (1)

Tim Biegeleisen
Tim Biegeleisen

Reputation: 521419

In this case, the boolean expressions will be treated as integers, with 0 representing false and 1 representing true. Then, your select:

SELECT ((new.fieldA IS NULL) + (new.fieldB IS NULL) + (new.fieldC IS NULL)) <> 2

will be true if only one of the three A, B, C fields is non null, with the other two being null. If all three are null, all are not null, or two are not null, then the condition would be false.

Upvotes: 1

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