在 SQL 加入中需要帮助

Question

我有两个 table 如下：

Table：员工

employeeid  code_one    code_two
101          17112       17112
102          17113       17112
103          17114       17112
104          17115       16800
106          17116       17112
107          17117       18000
108          17118       17112

Table: 代码

codeid  codename
17112   200TS
17113   400TS
17114   100TS
17115   500TS
17116   620TS
17117   899TS
17118   900TS
16800   888TS
18000   912TS

我需要这样的输出：输出

employeeid  code_one    code_two
101         200TS       200TS
102         400TS       200TS
103         100TS       200TS
104         500TS       888TS
106         620TS       200TS
107         899TS       912TS
108         900TS       200TS

我需要将员工 table 的代码 ID 与他们在代码 table 中的对应代码名称进行映射。请帮我。

Answer 1

您需要 join code table 两次。

SELECT E.employeeid,
       C.codename  AS code_one,
       C1.codename AS code_two
FROM   Employee E
       INNER JOIN Code C
               ON E.code_one = c.code
       INNER JOIN Code c1
               ON E.code_two = c.code

Answer 2

您只需要正确加入表格即可。

Table数据

SQL> SELECT * FROM employee;

EMPLOYEEID   CODE_ONE   CODE_TWO
---------- ---------- ----------
       101      17112      17112
       102      17113      17112
       103      17114      17112
       104      17115      16800
       106      17116      17112
       107      17117      18000
       108      17118      17112

7 rows selected.

SQL> SELECT * FROM code;

    CODEID CODENAME
---------- --------
     17112 200TS
     17113 400TS
     17114 100TS
     17115 500TS
     17116 620TS
     17117 899TS
     17118 900TS
     16800 888TS
     18000 912TS

9 rows selected.

查询

使用 Oracle 连接语法：

SQL> column code_one format a8
SQL> column code_two format a8
SQL> SELECT E.employeeid,
  2    C1.codename AS code_one,
  3    C2.codename AS code_two
  4  FROM Employee e,
  5    code c1,
  6    code c2
  7  WHERE E.code_one = c1.codeid
  8  AND E.code_two   = c2.codeid
  9  /

EMPLOYEEID CODE_ONE CODE_TWO
---------- -------- --------
       108 900TS    200TS
       106 620TS    200TS
       103 100TS    200TS
       102 400TS    200TS
       101 200TS    200TS
       104 500TS    888TS
       107 899TS    912TS

7 rows selected.

SQL>

使用 ANSI 连接语法：

SQL> SELECT E.employeeid,
  2    C1.codename AS code_one,
  3    C2.codename AS code_two
  4  FROM Employee e
  5  INNER JOIN code c1
  6  ON E.code_one = c1.codeid
  7  INNER JOIN code c2
  8  ON E.code_two = c2.codeid
  9  /

EMPLOYEEID CODE_ONE CODE_TWO
---------- -------- --------
       108 900TS    200TS
       106 620TS    200TS
       103 100TS    200TS
       102 400TS    200TS
       101 200TS    200TS
       104 500TS    888TS
       107 899TS    912TS

7 rows selected.

SQL>

在 SQL 加入中需要帮助

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