SQL INSERT/SELECT不在insert表中

Question

INSERT INTO     `tableA`
SELECT          `Col1`, 
                `Col2`,
                 NOW() 

FROM            `tableB`

WHERE           tableA.Col1 is not already in tableB.Col1

我无法正确获取WHERE子句以确保从tableA复制的记录只出现在表B中一次...

Answer 1

应该读:

tableA.col1不在其中(从表B中选择col1)