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  • mysql多表更新删除

    1、多表更新

    UPDATE
    table1 {[INNER]JOIN | {LEFT | RIGHT}[OUTER]JOIN} table2                                                                                                                                                                                                            
    ON conditional_ expr 
    SET col1 = {expr1 | DEFAULT}
    [,col2={expr2 | DEFAUL}]...
    [WHERE where_ condition]
    /*
    今天身份证号为210210199901012222的读者将超限的图书20151101归还,根据描述实现如下需求:
    1、更新借阅信息表,将借阅状态(status)更新为‘是’。
    2、更新罚款记录信息表,更新实际还书日期和罚款金额,罚款金额为每超出一天扣0.2元。
    3、同时更新读者信息表的余额。(在余额中扣除罚款金额)
    */
    
    UPDATE readerfee t1
    JOIN readerinfo t2 ON t1.card_id = t2.card_id
    SET actual_return_date = sysdate(),
     book_fee = datediff(sysdate(), return_date) * 0.2,
     balance = balance - book_fee
    WHERE
        t1.book_id = 20151101
    AND t1.card_id = '210210199901012222';

    2、多表删除

    DELETE table1[.*], table2[.*]
    
    FROM table1 {[INNER]JOIN | {LEFT| RIGHT}[OUTER]JOIN} table2 ON conditional_ expr
    
    [WHERE where_ condition]
    -- 1、由于业务需求,需要删除图书类别表中在图书信息表中没有图书记录的类别。
    SELECT
        book_id,
        book_name,
        category
    FROM
        bookcategory_bak t1
    LEFT JOIN bookinfo_bak t2 ON t1.category_id = t2.book_category_id
    WHERE
        parent_id <> 0;
    
    DELETE t1 FROM bookcategory_bak t1 LEFT JOIN bookinfo_bak t2 ON t1.category_id = t2.book_category_id WHERE parent_id <> 0 AND book_id IS NULL; SELECT * FROM bookcategory_bak; -- 2、需要删除图书类别表的编程语言的类别,以及图书信息表中关于编程语言的图书记录。 SELECT book_id, book_name, category_id, category FROM bookcategory_bak t1 INNER JOIN bookinfo_bak t2 ON t1.category_id = t2.book_category_id; DELETE t1, t2 FROM bookcategory_bak t1 INNER JOIN bookinfo_bak t2 ON t1.category_id = t2.book_category_id WHERE t1.category_id = 3;

    参考文档:https://blog.csdn.net/zdw19861127/article/details/80540124

    3、复制一张表:

    CREATE TABLE table1_bak
    AS
    SELECT * FROM table1;

    4、将查询的结果插入到一张表中:

    insert into table1 select * from table1_bak;
    
    insert into table1(字段1,字段2) select 字段m,字段n from  table2;
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  • 原文地址:https://www.cnblogs.com/zouhong/p/12770817.html
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