c# - 比较两张表并更新第三张

Question

假设我在 SQL “abc”中有一个表，其中有一列“数字”，该列包含 (1,2,3,4) 等。

在我的第二个表“xyz”中，我有一列“数字”，该列包含 (1,2,3,4,5,6,7,8,9)。

现在我想比较这两者并在第三个表中插入相等的数据。那么我该怎么做呢？

代码 ：

string str = "SELECT     Invoice_Details.PGI_ID, PARTY_BOOKING_DETAILS.PGI_ID AS abc ";
str += "FROM         PARTY_BOOKING_MAIN INNER JOIN ";
str += "    PARTY_BOOKING_DETAILS ON PARTY_BOOKING_MAIN.PBM_ID = PARTY_BOOKING_DETAILS.PBM_ID CROSS JOIN ";
str += "          Invoice_Details where PARTY_BOOKING_MAIN.PM_ID = 1 ";

SqlConnection con = new SqlConnection("data source = .; database = ePartyDatabase01; integrated security = true");
con.Open();
SqlCommand cmd1 = new SqlCommand("update Invoice_Details set [status] = @a", con);
SqlCommand cmd = new SqlCommand(str, con);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
    if (dr["PGI_ID"].ToString() == dr["abc"].ToString())
    {

        cmd1.Parameters.AddWithValue("@a", 1);

    }
}

dr.Close();
cmd1.ExecuteNonQuery();

con.Close();

Answer 1

您可能想要使用某种这样的查询：

insert into table3 (number)
select 
    t1.number
from abc t1
inner join xyz t2
    on t1.number = t2.number

Answer 2

我还没有测试过，但你可能甚至不需要 C#，试试这样的：

SELECT xyz.number
INTO third_table
FROM (
   SELECT t1.number
   FROM first_table t1 JOIN second_table t2 ON t1.number = t2.number
) AS xyz

Answer 3

也许是这样的：

INSERT INTO table3(number)
SELECT
    number
FROM
    xyz
WHERE NOT EXISTS
    (
        SELECT
            NULL
        FROM
            abc
        WHERE
            abc.number=xyz.number
    )