This works because TRUE is displayed as 1 in MySQL and FALSE as 0 . ... SELECT c.name, IF(a.addressid IS NULL,0,1) AS addressexists FROM ... ... <看更多>

I should think a table-level CHECK constraint would serve here, something like. CONSTRAINT c1_c2_null_match CHECK ((c1 IS NULL AND c2 IS ... ... <看更多>

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If you want to change the position of nulls in the results, you can use ISNULL(column) . The following query displays the number column in ... ... <看更多>