SET @row_number:=0;
SET @db_names:='';
SELECT @row_number:=CASE WHEN @db_names=app_id THEN @row_number+1 ELSE 1 END AS row_number,@db_names:=app_id AS db_names
FROM master_order
ORDER BY app_id ;
当我运行此语句时,它会给我结果。
我希望它像
select *from (SET @row_number:=0;
SET @db_names:='';
SELECT @row_number:=CASE WHEN @db_names=app_id THEN @row_number+1 ELSE 1 END AS row_number,@db_names:=app_id AS db_names
FROM master_order
ORDER BY app_id ) as temp
where row_number = 1;
我想选择重复列的第一行
答案 0 :(得分:0)
您可以像这样简化:
SELECT * FROM master_order
ORDER BY app_id = '' DESC, app_id
LIMIT 1;
但是为了澄清如果这种简化无法实现它将如何运作,或者这样:
SET @row_number:=0;
SET @db_names:='';
select *from (
SELECT @row_number:=CASE WHEN @db_names=app_id THEN @row_number+1 ELSE 1 END AS row_number,@db_names:=app_id AS db_names
FROM master_order
ORDER BY app_id
) as temp
where row_number = 1;
或者这个:
select *from (
SELECT @row_number:=CASE WHEN @db_names=app_id THEN @row_number+1 ELSE 1 END AS row_number,@db_names:=app_id AS db_names
FROM master_order
CROSS JOIN (SELECT @row_number := 0, @db_names := '') var_init
ORDER BY app_id
) as temp
where row_number = 1;