如果有兩個左連接，如何從左表中獲取所有行

Question

我在 mysqli 查詢中添加了兩個左連接，我需要第一個表 audit_form_tbl 中的所有行。

SELECT qt1.field_id
     , qt1.type
     , qt1.parent_id
     , qt1.field_type
     , qt1.field_name
     , qt1.required
     , qt1.maxlength
     , qft1.field_value
     , qt1.can_be_na
     , qft1.form_id
     , avtf.type_variable 
  FROM audit_form_tbl qt1 
  LEFT 
  JOIN audit_variables_tbl avtf 
    ON qt1.audit_variable_id = avtf.id 
  JOIN audit_form_value_4_tbl qft1 
    ON qt1.field_id = qft1.field_id 
 WHERE qt1.field_id = qft1.field_id 
   AND qt1.type IN ('F') 
   AND avtf.company_id IN ('4', 0) 
   AND qt1.company_form_id = '23' 
   AND qft1.form_id = '4231578043277' 
   AND qt1.parent_id = '' 
   AND qt1.status = 1 
ORDER 
   BY qt1.sort_order ASC

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審計表單表有一些沒有插入 audit_value_tbl 的行。 我只獲取已插入 audit_value_tbl 表中的行。

Answer 1

SELECT qt1.field_id
     , qt1.type
     , qt1.parent_id
     , qt1.field_type
     , qt1.field_name
     , qt1.required
     , qt1.maxlength
     , qft1.field_value
     , qt1.can_be_na
     , qft1.form_id
     , avtf.type_variable 
  FROM audit_form_tbl qt1 
  LEFT 
  JOIN audit_variables_tbl avtf 
    ON qt1.audit_variable_id = avtf.id 
   AND avtf.company_id IN (4,0) 
  LEFT -- <-- obviously, omit this if you want an INNER JOIN here
  JOIN audit_form_value_4_tbl qft1 
    ON qt1.field_id = qft1.field_id
   AND qft1.form_id = '4231578043277' 
   AND qt1.field_id = qft1.field_id 
 WHERE qt1.type IN ('F') 
   AND qt1.company_form_id = 23 
   AND qt1.parent_id = '' 
   AND qt1.status = 1 
ORDER 
   BY qt1.sort_order ASC