MySql重寫子查詢加入

Question

我對此查詢有疑問：

SELECT Group_concat(DISTINCT titlegredcd) 
       targetGroup, 
       tblevent.id, 
       generalsubcategorynm, 
       generalcategorynm, 
       coursename, 
       (SELECT Count(*) 
        FROM   tblinternalstudent, 
               tblstaff 
        WHERE  eventid = tblevent.id 
               AND tblinternalstudent.staffnoic = tblstaff.staffnoic) Total, 
       Date_format(startdate, '%d %b') 
       startdateDisplay, 
       Date_format(enddate, '%d %b') 
       enddateDisplay, 
       class, 
       organizer, 
       subcategorymainorder, 
       subcategorysuborder, 
       tblrefgeneralsubcategory.generalcategorycd, 
       tblrefgeneralsubcategory.generalsubcategorycd 
FROM   tblevent, 
       tblcourse, 
       tblrefgeneralsubcategory, 
       tblrefgeneralcategory, 
       tblinternalstudent a, 
       tblstaff b 
WHERE  tblrefgeneralsubcategory.generalcategorycd IN 
       ( 'G0001', 'G0002', 'G0003' ) 
       AND tblcourse.generalcategorycd = 
           tblrefgeneralsubcategory.generalcategorycd 
       AND tblcourse.generalsubcategorycd = 
           tblrefgeneralsubcategory.generalsubcategorycd 
       AND tblevent.courseid = tblcourse.courseid 
       AND tblrefgeneralsubcategory.generalcategorycd = 
           tblrefgeneralcategory.generalcategorycd 
       AND a.eventid = tblevent.id 
       AND a.staffnoic = b.staffnoic 
       AND startdate >= '2012-01-01' 
       AND enddate <= '2012-12-31' 
GROUP  BY tblevent.id, 
          generalsubcategorynm, 
          generalcategorynm, 
          coursename, 
          total, 
          startdatedisplay, 
          enddatedisplay, 
          class, 
          organizer, 
          subcategorymainorder, 
          subcategorysuborder, 
          tblrefgeneralsubcategory.generalcategorycd, 
          tblrefgeneralsubcategory.generalsubcategorycd 
ORDER  BY tblrefgeneralsubcategory.generalsubcategorycd, 
          coursename 

處理大約需要30分鍾，我懷疑問題來自於子選擇。

我嘗試使用連接重寫：

SELECT e.id, 
       e.courseid, 
       internalstaff.targetgroup, 
       internalstaff.total, 
       Date_format(startdate, '%d %b') AS startdateDisplay, 
       Date_format(enddate, '%d %b')   AS enddateDisplay, 
       class, 
       organizer, 
       coursename, 
       gs.generalcategorycd, 
       gs.generalsubcategorycd, 
       gs.generalsubcategorynm, 
       gs.subcategorymainorder, 
       gs.subcategorysuborder, 
       generalcategorynm 
FROM   tblcourse c, 
       tblrefgeneralsubcategory gs, 
       tblrefgeneralcategory g, 
       tblevent e 
       JOIN (SELECT i.eventid, 
                    Count(*)                           AS Total, 
                    Group_concat(DISTINCT titlegredcd) AS TargetGroup 
             FROM   tblinternalstudent i, 
                    tblstaff s 
             WHERE  i.staffnoic = s.staffnoic 
             GROUP  BY i.eventid) AS internalstaff 
         ON internalstaff.eventid = e.id 
WHERE  e.courseid = c.courseid 
       AND gs.generalcategorycd = g.generalcategorycd 
       AND gs.generalcategorycd IN ( 'G0001', 'G0002', 'G0003' ) 
       AND c.generalcategorycd = gs.generalcategorycd 
       AND c.generalsubcategorycd = gs.generalsubcategorycd 
       AND startdate >= '2012-01-01' 
       AND enddate <= '2012-12-31' 
GROUP  BY e.id, 
          generalsubcategorynm, 
          generalcategorynm, 
          startdatedisplay, 
          enddatedisplay, 
          class, 
          organizer, 
          subcategorymainorder, 
          subcategorysuborder, 
          generalcategorycd, 
          generalsubcategorycd 
ORDER  BY generalsubcategorycd, 
          coursename 

它加載速度更快，並返回正確數量的記錄作為原始查詢（1802）。 但是，當我在internalstaff表中添加BranchCd（和branchcd =“某些分支代碼”）時，它將返回較少的記錄數（519）。

但是在原始查詢中，如果將（和branchcd ='some branch code'）添加到子選擇中，它將返回正確的記錄數。

任何人都可以提出關於如何重寫聯接以使其像子選擇一樣工作的建議嗎？

謝謝。

編輯：很抱歉忘記包含表格：

tblinternalstudent (**staffnoic**, eventid)
tblstaff (**staffnoic** titlegredcd, branchcd, unitcd)
tblevent (**id**, courseid, startdate, enddate, class, organizer)
tblcourse (**courseid**, coursename)
tblrefgeneralcategory (**generalcategorycd**, generalcategorynm)
tblrefgeneralsubcategory (**generalsubcategorycd, generalsubcategorynm, generalcategorycd,subcategorymainorder, subcategorysuborder)

原始查詢的解釋：

*************************** 1. row ***************************
       id: 1
       select_type: PRIMARY
       table: a
       type: ALL
       possible_keys: NULL
       key: NULL
       key_len: NULL
       ref: NULL
       rows: 38760
       Extra: Using temporary; Using filesort
*************************** 2. row ***************************
       id: 1
       select_type: PRIMARY
       table: b
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 44
       ref: edu_db.a.StaffNoIC
       rows: 1
       Extra: Using where
*************************** 3. row ***************************
       id: 1
       select_type: PRIMARY
       table: tblEvent
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 32
       ref: edu_db.a.EventId
       rows: 1
       Extra: Using where
*************************** 4. row ***************************
       id: 1
       select_type: PRIMARY
       table: tblcourse
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 30
       ref: edu_db.tblEvent.courseid
       rows: 1
       Extra: Using where
*************************** 5. row ***************************
       id: 1
       select_type: PRIMARY
       table: tblRefGeneralSubCategory
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 34
       ref: edu_db.tblcourse.GeneralSubCategoryCd,edu_db.tblcourse.GeneralCategoryCd
       rows: 1
       Extra:
*************************** 6. row ***************************
       id: 1
       select_type: PRIMARY
       table: tblRefGeneralCategory
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 17
       ref: edu_db.tblcourse.GeneralCategoryCd
       rows: 1
       Extra:
*************************** 7. row ***************************
       id: 2
       select_type: DEPENDENT SUBQUERY
       table: tblinternalstudent
       type: ALL
       possible_keys: NULL
       key: NULL
       key_len: NULL
       ref: NULL
       rows: 38760
       Extra: Using where
*************************** 8. row ***************************
       id: 2
       select_type: DEPENDENT SUBQUERY
       table: tblStaff
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 44
       ref: edu_db.tblinternalstudent.StaffNoIC
       rows: 1
       Extra: Using where; Using index

第二個查詢的解釋：

*************************** 1. row ***************************
       id: 1
       select_type: PRIMARY
       table: <derived2>
       type: ALL
       possible_keys: NULL
       key: NULL
       key_len: NULL
       ref: NULL
       rows: 8849
      Extra: Using temporary; Using filesort
*************************** 2. row ***************************
       id: 1
       select_type: PRIMARY
       table: e
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 32
       ref: internalstaff.eventid
       rows: 1
      Extra: Using where
*************************** 3. row ***************************
       id: 1
       select_type: PRIMARY
       table: c
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 30
       ref: edu_db.e.courseid
       rows: 1
       Extra: Using where
*************************** 4. row ***************************
       id: 1
       select_type: PRIMARY
       table: gs
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 34
       ref: edu_db.c.GeneralSubCategoryCd,edu_db.c.GeneralCategor
       rows: 1
       Extra:
*************************** 5. row ***************************
       id: 1
       select_type: PRIMARY
       table: g
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 17
       ref: edu_db.gs.GeneralCategoryCd
       rows: 1
       Extra: Using where
*************************** 6. row ***************************
       id: 2
       select_type: DERIVED
       table: i
       type: ALL
       possible_keys: NULL
       key: NULL
       key_len: NULL
       ref: NULL
       rows: 38760
       Extra: Using filesort
*************************** 7. row ***************************
       id: 2
       select_type: DERIVED
       table: s
       type: eq_ref
       possible_keys: PRIMARY
       key: PRIMARY
       key_len: 44
       ref: edu_db.i.StaffNoIC
       rows: 1

Answer 1

嘗試使用此查詢還可能存在一些關聯問題，因為您在此處未明確告知。

SELECT
  te.id,
  Date_format(startdate, '%d %b') AS startdateDisplay,
  Date_format(enddate, '%d %b') AS enddateDisplay,
  te.class,
  te.organizer,
  tgs.generalcategorycd,
  tgs.generalsubcategorycd,
  tgs.generalsubcategorynm,
  tgs.subcategorymainorder,
  tgs.subcategorysuborder,
  trc.generalcategorynm,
  count(tic.*)             AS `Total`,
  GROUP_CONCAT(DISTINCT tic. titlegredcd) AS TargetGroup
FROM tblevent AS te
  LEFT JOIN tblinternalstudent AS tis
    ON tis.eventid = te.id
  LEFT JOIN tblstaff AS ts
    ON ts.staffnoic = tis.staffnoic
  LEFT JOIN tblcourse AS tc
    ON tc.courseid = te.courseid
  LEFT JOIN tblrefgeneralsubcategory AS tgs
    ON tgs.generalcategorycd = tc.generalcategorycd
  LEFT JOIN tblrefgeneralcategory AS trc
    ON trc.generalcategorycd = tgs.generalcategorycd
WHERE te.startdate >= '2012-01-01'
    AND te.enddate <= '2012-12-31'
    AND trc.generalcategorycd IN('G0001', 'G0002', 'G0003')
GROUP BY te.id, tgs.generalsubcategorynm, trc.generalcategorynm, te.startdatedisplay, te.enddatedisplay te.class, te.organizer, tgs.subcategorymainorder, tgs.subcategorysuborder, trc.generalcategorycd, tgs.generalsubcategorycd
ORDER BY tgs.generalsubcategorycd, tc.coursename