在SQL Server中加入2个表

Question

我有两张表如下：

TABLE_1

    CODE1    CODE2     CODE3    SYNC
    -----------------------------------
    02       03         04         YES
    01       03         NULL         NO
    01       02         03         NA

TABLE_2

    CODE     NAME
    --------------
    01       ABC
    02       BCD
    03       DEF
    04       EFG

如何创建查询，如下所示：

    CODE1     CODE2       CODE3      SYNC
    --------------------------------------
    BCD       DEF         EFG         YES
    ABC       DEF         NULL        NO
    ABC       BCD         DEF         NA

Answer 1

这是你需要做的事情

SELECT T2.CODE AS [CODE1],T3.CODE AS [CODE2],T4.CODE AS [CODE3],T.SYNC
FROM Table_1 T
LEFT JOIN Table_2 T2 ON T2.CODE = T.CODE1
LEFT JOIN Table_2 T3 ON T3.CODE = T.CODE2
LEFT JOIN Table_2 T4 ON T4.CODE = T.CODE3

Answer 2

尝试使用left join：

SELECT
    tblCODE1.NAME AS CODE1,
    tblCODE2.NAME AS CODE2,
    tblCODE3.NAME AS CODE3,
    Table_1.SYNC
FROM
    Table_1
    LEFT JOIN Table_2 as tblCODE1
        ON tblCODE1.CODE=Table_1.CODE1
    LEFT JOIN Table_2 as tblCODE2
        ON tblCODE2.CODE=Table_1.CODE2
    LEFT JOIN Table_2 as tblCODE3
        ON tblCODE3.CODE=Table_1.CODE3