在 SQL 查询中使用变量

Question

我正在使用 MySql 数据库。我进行了以下查询并在提示符下运行，它运行正常。

SELECT 
    tr_date,
    tr_invno,
    particulars,
    received,
    issued, 
       @running_total:=@running_total + t.balance AS running_balance
FROM
(SELECT 
    srno,
    tr_date,
    tr_invno,
    tr_type,
    tr_accounthead as particulars,
    case when tr_type=1 then tr_qty else 0 end received,
    case when tr_type=2 then tr_qty else 0 end issued, 
    case when tr_type=1 then tr_qty else -(tr_qty) end balance 
    FROM tblinvtransaction where tr_date between '2021-09-01' and '2021-09-09' and tr_itemcode = '01') t
JOIN (SELECT @running_total:=(select sum(case when tr_type='1' then tr_qty else -(tr_qty) end) from tblinvtransaction where tr_date<'2021-09-01' and tr_itemcode = '01')
) r
ORDER BY t.tr_date, t.tr_type

但是当我在 C# 中使用它时，它给出错误“在命令执行期间遇到致命错误”

        string query = @"SELECT tr_date, tr_invno, particulars, received, issued, @running_total:= @running_total + t.balance AS running_balance 
            FROM(SELECT srno, tr_date, tr_invno, tr_type, tr_accounthead as particulars,
                case when tr_type = 1 then tr_qty else 0 end received,
                case when tr_type = 2 then tr_qty else 0 end issued,
                case when tr_type = 1 then tr_qty else -(tr_qty)end balance
                FROM tblinvtransaction where tr_date between '2021-09-01' and '2021-09-09' and tr_itemcode = '01') t
            JOIN(SELECT @running_total:= (select sum(case when tr_type = '1' then tr_qty else -(tr_qty)end) from tblinvtransaction where tr_date < '2021-09-01' and tr_itemcode = '01')
            ) r
            ORDER BY t.tr_date, t.tr_type)";
        string MySql = string.Concat(query);
        MySqlDataAdapter da = new MySqlDataAdapter(MySql, connection);
        DS_ItemLedger ds = new DS_ItemLedger();
        da.Fill(ds, "DT_ItemLedger");

请指导。

Answer 1

MySqlCommand 默认情况下通常不允许在 SQL 语句中使用用户变量。要启用此功能，您必须将Allow User Variables = true; 添加到您的连接字符串中。详情请见https://mysqlconnector.net/connection-options/#AllowUserVariables。

它应该适用于 MySql.Data，但您可能必须从 MySql.Data 切换到 MySqlConnector 才能完全正常工作。

Answer 2

你不能在原始查询中声明变量 所以，你应该创建一个存储过程，并在你的代码中调用它

Answer 3

你能做到吗？

SELECT 
    tr_date,
    tr_invno,
    particulars,
    received,
    issued, 
    running_total + t.balance AS running_balance
FROM
(SELECT 
    srno,
    tr_date,
    tr_invno,
    tr_type,
    tr_accounthead as particulars,
    case when tr_type=1 then tr_qty else 0 end received,
    case when tr_type=2 then tr_qty else 0 end issued, 
    case when tr_type=1 then tr_qty else -(tr_qty) end balance,
    (select sum(case when tr_type='1' then tr_qty else -(tr_qty) end) from tblinvtransaction where tr_date<'2021-09-01' and tr_itemcode = '01') as running_total
    FROM tblinvtransaction where tr_date between '2021-09-01' and '2021-09-09' and tr_itemcode = '01') t
ORDER BY t.tr_date, t.tr_type

Answer 4

我找到了替代解决方案：

1。 选择 srno, tr_date, tr_invno, tr_type, tr_accounthead 作为详细信息， 当 tr_type=1 然后 tr_qty else 0 end 收到时， 如果 tr_type=2 然后 tr_qty else 0 end 发出， sum（当 tr_type=1 然后 tr_qty else -(tr_qty) end) over (order by tr_date, srno rows unbounded before)+4 as running_total FROM tblinvtransaction 其中 tr_date 在 '2021-09-01' 和 '2021-09-09' 之间且 tr_itemcode = '02' ORDER BY tr_date, tr_type

2。 选择 srno, tr_date, tr_invno, tr_type, tr_accounthead 作为详细信息， 当 tr_type=1 然后 tr_qty else 0 end 收到时， 当 tr_type=2 然后 tr_qty else 0 end 发出的情况 ,( SELECT SUM（当 tr_type=1 然后 tr_qty else -(tr_qty) end 时的情况） FROM tblinvtransaction 作为 A WHERE A.srno FROM tblinvtransaction AS B WHERE B.tr_itemcode ='01' 由 B.srno 订购