使用LEFT OUTER JOIN ORACLE SQL将一个表连接到多个表

Question

    SELECT DISTINCT  'DATA'          AS DSN,
'MASTER' AS ORG_ID,e.emp_id,
  e.emp_name                                  AS EMPLOYEE_NUMBER,
  e.emp_firstname                             AS EMPLOYEE_FIRST_NAME,
  e.emp_lastname                              AS EMPLOYEE_LAST_NAME,
  e.emp_val20                                 AS PAY_STATUS,
  (NVL(TO_CHAR(PGT.PAYGRPTYP_NAME),'MASTER')) AS PAY_FREQUENCY,
  E.EMP_VAL16                                 AS PAY_CLASS,
  SP.SHFTPAT_NAME                             AS SHIFT_CODE,
  WB.WBU_EMAIL                                AS EMAIL_ADDR,
  (NVL(TO_CHAR( DE.DEPT_NAME),'MASTER'))      AS DEPARTMENT,
  NULL                                        AS HELD_POSTN,
  (NVL(TO_CHAR( J.JOB_NAME),'MASTER'))        AS JOB_TITLE,
  WB. WBU_NAME                                AS USER_NAME,
  (NVL(TO_CHAR(ET.WBT_ID ),'MASTER'))         AS TEAM_CODE,
  WT.WBT_NAME                                 AS TEAM_NAME,
  WT.WBT_DESC                                 AS TEAM_DESC,
(NVL(TO_CHAR(EB.EMPBDG_BADGE_NUMBER),'MASTER'))          AS PERMANENT_BADGE_NO
FROM EMPLOYEE E
LEFT  JOIN SHIFT_PATTERN SP
ON E.SHFTPAT_ID =SP.SHFTPAT_ID
LEFT  JOIN PAY_GROUP PT
ON E.PAYGRP_ID =PT.PAYGRP_ID
LEFT  JOIN PAY_GROUP_TYPE PGT
ON PT.PAYGRPTYP_ID =PGT.PAYGRPTYP_ID
LEFT  JOIN EMPLOYEE_BADGE EB
ON E.EMP_ID=EB.EMP_ID
LEFT  JOIN EMP_UDF_DATA ED
ON E.EMP_ID=ED.EMP_ID
LEFT  JOIN WORKBRAIN_USER WB
ON E.EMP_ID=WB.EMP_ID
LEFT  JOIN EMP_DEF_LAB D
ON E.EMP_ID=D.EMP_ID
LEFT  JOIN DEPARTMENT DE
ON D.DEPT_ID=DE.DEPT_ID
LEFT  JOIN EMPLOYEE_JOB EJ
ON E.EMP_ID=EJ.EMP_ID
LEFT  JOIN JOB J
ON EJ.JOB_ID=J.JOB_ID
LEFT  JOIN EMPLOYEE_TEAM ET
ON E.EMP_ID=ET.EMP_ID
LEFT  JOIN WORKBRAIN_TEAM WT
ON ET.WBT_ID=WT.WBT_ID
LEFT  JOIN CALC_GROUP CG
ON E.CALCGRP_ID     =CG.CALCGRP_ID
WHERE E.EMP_ID NOT IN (SELECT EMP_ID FROM EMPLOYEE_READER_GROUP)
AND sysdate BETWEEN ET.empt_start_date AND ET.empt_end_date
AND ET.empt_home_team = 'Y'
AND sysdate BETWEEN EJ.EMPJOB_START_DATE AND EJ.EMPJOB_END_DATE
GROUP BY E.EMP_ID,
  -- ER.rdrgrp_id,
  e.emp_name,
  e.emp_lastname,
  e.emp_firstname,
  e.emp_status,
  e.emp_val20,
  PGT.PAYGRPTYP_NAME,
  E.EMP_VAL16,
  e.EMP_VAL18,
  EB.EMPBDG_BADGE_NUMBER,
  WB.WBU_EMAIL,
  DE.DEPT_NAME,
  J.JOB_NAME,
  SP.SHFTPAT_NAME,
  WB. WBU_NAME ,
  ET.WBT_ID ,
  WT.WBT_NAME,
 WT.WBT_DESC;

我想要从employee表中获取所有数据，所以我使用了左联接，但是我没有获取到employee表中所有可用的行，某些值丢失了。请帮助我。 我的员工有43000行，但是当我使用它时，我仅获得17000行。 我不确定我在哪里落后。我想要空列作为Master来获得正确的表值。

Answer 1

您可以整天不停地加入，您的where子句仍将充当过滤器。 尝试使用不带where子句的示例，看看是否能获得全部43k。 另外，您正在分组，这可能会使行崩溃。

Answer 2

WHERE子句中的这些过滤器将OUTER JOIN转换为INNER JOIN：

AND sysdate BETWEEN ET.empt_start_date AND ET.empt_end_date
AND ET.empt_home_team = 'Y'
AND sysdate BETWEEN EJ.EMPJOB_START_DATE AND EJ.EMPJOB_END_DATE

因为它们排除了测试属性为null的行（这是它们在不匹配的外部联接行中的含义）。

因此，有两种方法。 首先是允许空值，例如

AND ( ET.empt_home_team  is null or 
     ( sysdate BETWEEN ET.empt_start_date AND ET.empt_end_date
       AND ET.empt_home_team = 'Y' )
    )
AND ( EJ.EMPJOB_START_DATE is null 
      or sysdate BETWEEN EJ.EMPJOB_START_DATE AND EJ.EMPJOB_END_DATE )

第二是用内联视图替换表，例如

LEFT  JOIN ( select * from EMPLOYEE_TEAM
            where sysdate BETWEEN empt_start_date AND empt_end_date
            AND empt_home_team = 'Y' ) ET
   ON E.EMP_ID=ET.EMP_ID
LEFT  JOIN ( select * from EMPLOYEE_JOB
            where sysdate BETWEEN EMPJOB_START_DATE AND EMPJOB_END_DATE ) EJ
   ON E.EMP_ID=EJ.EMP_ID

哪种方法更适合您取决于数据。 测试他们，看看。

Answer 3

考虑一下您想要的数据集。 当您左联接时，实际上只需要其中之一的数据就可以联接整个表。 我已经修改了一些您的LEFT JOINS来考虑这一点。 同样，在大型数据集上执行WHERE x NOT IN（SELECT x ....）可能非常慢。 我已经对其进行了更改，以使优化器可以更好地工作。 现在，它执行LEFT JOIN .... WHERE x IS NULL。 这应该可以更快地工作。 您对MAXing有什么计划？ 这个查询非常复杂。 您想要确保在获取所需的初始数据之前尝试对其进行汇总。

SELECT 'DATA'                                 AS DSN,
  'MASTER' AS ORG_ID,e.emp_id,
  e.emp_name                                  AS EMPLOYEE_NUMBER,
  e.emp_firstname                             AS EMPLOYEE_FIRST_NAME,
  e.emp_lastname                              AS EMPLOYEE_LAST_NAME,
  e.emp_val20                                 AS PAY_STATUS,

  (NVL(TO_CHAR(ptpgt.PAYGRPTYP_NAME),'MASTER')) AS PAY_FREQUENCY, /* From subquery join */

  E.EMP_VAL16                                 AS PAY_CLASS,

  SP.SHFTPAT_NAME                             AS SHIFT_CODE,

  WB.WBU_EMAIL                                AS EMAIL_ADDR,

  (NVL(TO_CHAR( DE.DEPT_NAME),'MASTER'))      AS DEPARTMENT,

  NULL                                        AS HELD_POSTN,
  (NVL(TO_CHAR( eej.JOB_NAME),'MASTER'))      AS JOB_TITLE, /* From subquery join */
  WB. WBU_NAME                                AS USER_NAME,
  (NVL(TO_CHAR(eet.WBT_ID ),'MASTER'))        AS TEAM_CODE, /* From subquery join */

  WT.WBT_NAME                                 AS TEAM_NAME,
  WT.WBT_DESC                                 AS TEAM_DESC,

  (NVL(TO_CHAR(EB.EMPBDG_BADGE_NUMBER),'MASTER')) AS PERMANENT_BADGE_NO

FROM EMPLOYEE E
/* This plus WHERE ERG.EMP_ID IS NULL is the same as the subquery filter. But faster. */
LEFT OUTER JOIN EMPLOYEE_READER_GROUP erg ON e.EMP_ID = ERG.EMP_ID 

LEFT  JOIN SHIFT_PATTERN SP ON E.SHFTPAT_ID =SP.SHFTPAT_ID

LEFT  JOIN (
    SELECT PT.EMP_ID,PGT.PAYGRPTYP_NAME
    FROM PAY_GROUP PT 
    INNER JOIN PAY_GROUP_TYPE PGT ON PT.PAYGRPTYP_ID =PGT.PAYGRPTYP_ID
) ptpgt ON E.PAYGRP_ID =ptpgt.PAYGRP_ID
LEFT  JOIN EMPLOYEE_BADGE EB ON E.EMP_ID=EB.EMP_ID
LEFT  JOIN EMP_UDF_DATA ED ON E.EMP_ID=ED.EMP_ID
LEFT  JOIN WORKBRAIN_USER WB ON E.EMP_ID=WB.EMP_ID
LEFT  JOIN ( 
    SELECT D.EMP_ID, DE.DEPT_NAME 
    FROM EMP_DEF_LAB D 
    INNER JOIN DEPARTMENT DE ON D.DEPT_ID=DE.DEPT_ID
) dde ON E.EMP_ID=dde.EMP_ID
LEFT  JOIN ( 
    SELECT EJ.EMP_ID, J.JOB_NAME
    FROM EMPLOYEE_JOB EJ 
    INNER JOIN JOB J ON EJ.JOB_ID=J.JOB_ID
    WHERE sysdate BETWEEN EJ.EMPJOB_START_DATE AND EJ.EMPJOB_END_DATE
        /* 
            Doublecheck your date filters. Are they getting the edge dates you need?
            BETWEEN makes it easy to miss a date, especially if your fields
            are DATETIME datatypes. 
            USE <=/>= to be a bit clearer.
        */
  ) eej ON E.EMP_ID=eej.EMP_ID

LEFT  JOIN (
    SELECT ET.EMP_ID, WBT_ID
    FROM EMPLOYEE_TEAM ET 
    INNER JOIN WORKBRAIN_TEAM WT ON ET.WBT_ID=WT.WBT_ID
    WHERE 
        ET.empt_home_team = 'Y'
        AND sysdate BETWEEN ET.empt_start_date AND ET.empt_end_date
        /* 
            Doublecheck your date filters. Are they getting the edge dates you need?
            BETWEEN makes it easy to miss a date, especially if your fields
            are DATETIME datatypes. 
            USE <=/>= to be a bit clearer.
        */
) eet ON E.EMP_ID=eet.EMP_ID

LEFT  JOIN CALC_GROUP CG ON E.CALCGRP_ID=CG.CALCGRP_ID

WHERE 
    ERG.EMP_ID IS NULL