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[英]Problem when using CASE function in mysql but getting Error Code: 1241. Operand should contain 1 column(s)
[英]Using a sp with an out variable get the following error message: Error Code: 1241. Operand should contain 1 column(s)
我在MySql中編寫了一個存儲過程,其中包含一個out變量,但是當我要調用它時,出現以下錯誤。 有人可以幫我了解我在做什么錯嗎? 這是sp:
CREATE DEFINER=`root`@`localhost` PROCEDURE `storedp2`(out shift nvarchar(40))
begin
set shift= (SELECT * FROM myblog.computed);
end
這就是我所說的:
set @test='';
call storedp2 (@test) ;
select @test as t;
這是錯誤:
錯誤代碼:1241。操作數應包含1列
您需要返回單個值:
CREATE DEFINER=`root`@`localhost` PROCEDURE `storedp2`(out shift nvarchar(40))
begin
set shift= (SELECT col_name FROM myblog.computed WHERE id = ?);
-- (single column/single row)
-- set shift = (SELECT col_name FROM myblog.computed WHERE ... LIMIT 1);
end;
您不能將SELECT * FROM tab
結果分配給NVARCHAR(40)
:
scalar := (col1, col2, col3) -- won't work (multiple cols, single row)
scalar := (col1, col2), (col1, col2) -- won't work (multiple cols, multiple rows)
sclara := (col1), (col1) -- won't work (single col, multiple rows)
編輯:
如果我想返回整個選擇的情感該怎么辦
CREATE DEFINER=`root`@`localhost` PROCEDURE `storedp2`()
begin
-- some logic
SELECT * FROM myblog.computed;
end
call storedp2 ();
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