mysql where條件基於左聯接字段

Question

我正在研究一個邏輯，如果LEFT聯合字段為null，則不應應用Where中的條件。 有人可以告訴我如何僅通過查詢來完成。

我嘗試使用IF CASE，但沒有幫助，

查詢：

SELECT *
FROM tableA ta
LEFT JOIN tableB tb ON tb.id = ta.id_c
WHERE ta.sales = 'Closed'
  AND tb.deleted=0

當ta.id_c為null時， 不應考慮AND tb.deleted = 0的條件。

為什么？ 因為當鏈接ID中的值為空時，將沒有查詢數據的選擇。 有什么幫助嗎？ 提前致謝。

預期結果：選擇表的列。

實際表：

tableA：

id_c    sales  
   1    Closed 
   2    Closed 

tableB：

   id  deleted 
   1    0 

查詢后：當前

id_c    sales   id  deleted 
   1    Closed  1   0

預期

id_c    sales   id    deleted 
   1    Closed  1       0
   2    Closed  NULL   NULL

注意：我無法編輯LEFT JOIN條件

Answer 1

給定

create table tableA (
  id_c integer,
  sales varchar(255)
);

create table tableB (
  id integer,
  deleted bool
);

insert into tableA values (1, 'Closed'), (2, 'Closed');
insert into tableB values (1, 0);

SELECT *
FROM tableA ta
LEFT JOIN tableB tb ON tb.id = ta.id_c
WHERE
  (ta.sales = 'Closed' AND tb.deleted = 0) OR
  (ta.sales = 'Closed' AND tb.id is null)

或少一點羅word

WHERE
  (ta.sales = 'Closed') AND (tb.deleted = 0 OR tb.id is null);

結果是

id_c    sales   id  deleted 
1   Closed  1   0
2   Closed  NULL    NULL