mySQL有條件加入Query Quary cupareization

，可以根據指示表的字段的字段的值執行連接的值。 While switch-case statements cannot be directly employed in SQL queries, there are alternative methods to achieve conditional joins.

Solution

To execute a conditional join in MySQL, you can utilize multiple LEFT JOIN statements with conditions that specify the target table based on the value of the "type" field.以下是一個示例：

中，查詢從“ t”表中選擇“ id”和“ type”字段。 “ type”值是't2'。 它可以通過“ t3”表，連接“ t.id”等於“ t3.id”的記錄，並且只有當“ type”值是't3.id'等於't3.id。不必要的加入。