Insert into t1(col1,col2,col3)
select
t2.col1,
t2.col2,
t3.col2
from
table2 t2 left outer join
table3 t3
on t2.col1=t3.col1
这是我的代码的基础知识。如何检查插入的数据是否已经存在?
答案 0 :(得分:0)
您可以使用
if(not exists (select col1 from t1 where col1 in(select
t2.col1
from
table2 t2 left outer join
table3 t3
on t2.col1=t3.col1)))
Begin
Insert into t1(col1,col2,col3)
select
t2.col1,
t2.col2,
t3.col2
from
table2 t2 left outer join
table3 t3
on t2.col1=t3.col1
end
ps这里只检查col1数据,你可以添加col2和col3
答案 1 :(得分:0)
使用SQL EXISTS运算符
INSERT INTO t1
( col1 ,
col2 ,
col3
)
SELECT t2.col1 ,
t2.col2 ,
t3.col2
FROM table2 t2
LEFT OUTER JOIN table3 t3 ON t2.col1 = t3.col1
WHERE NOT EXISTS ( SELECT 1
FROM T1
WHERE t1.col1 = t2.col1
AND t1.col2 = t2.col2
AND t1.col3 = t3.col2 )