資料庫中表的複雜查詢，資料庫中表複雜

資料庫中表的複雜查詢，資料庫中表複雜

資料庫中表的複雜查詢1、串連查詢1.0串連的基本文法格式：from TABLE1 join_type TABLE2 [on (join_condition)][where (query_condition)]TABLE1:左表TABLE2：右表join_type：串連的類型。交叉、內串連、左外串連、右外串連on：設定串連條件where：對串連查詢的結果進步一的篩選1.1交叉串連select * from CUSTOMER cross join ORDERS;或者select * from CUSTOMER,ORDERS;select c.name,o.order_number from CUSTOMER c,ORDERS o;1.2內串連：隱式內串連：(不使用on關鍵字，使用where)select * from CUSTOMER c,ORDERS o where c.id=o.customer_id;顯式內串連：(使用on關鍵字)select * from CUSTOMER c inner join ORDERS o on c.id=o.customer_id;1.3外串連：左外串連：(返回符合串連條件的所有記錄，同時還返回左表中其餘的所有記錄)select * from CUSTOMER c left outer join ORDERS o on c.id=o.customer_id;右外串連：(返回符合串連條件的所有記錄，同時還返回右表中其餘的所有記錄)select * from CUSTOMER c right outer join ORDERS o on c.id=o.customer_id;2、子查詢（巢狀查詢）子查詢： select * from orders where customer_id=(select id from customer where name='張三');3、聯集查詢SELECT * FROM orders WHERE price>200 UNION SELECT * FROM orders WHERE customer_id=1;取兩條語句的並集，並去除重複的記錄。

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