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smallkun 2025-02-21 11:26:27 +08:00
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2208/天天乐学考试答案/MySQL练习（一）.md
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@ -27,5 +27,31 @@ REFERENCES 表名(字段) 字段是表中的主键
ALTER TABLE 表名 ADD CONSTRAINT 外键名 FOREIGN KEY(字段名) REFERENCES 表名(主键字段名); ALTER TABLE 表名 ADD CONSTRAINT 外键名 FOREIGN KEY(字段名) REFERENCES 表名(主键字段名);
ALTER TABLE t_employee ADD CONSTRAINT fK_did FOREIGN KEY(did) REFERENCES t_department(did); ALTER TABLE t_employee ADD CONSTRAINT fK_did FOREIGN KEY(did) REFERENCES t_department(did);
#4 排序、分页查询
/*
基础查询
SELECT 字段
FROM 表
ORDER BY 需要排序的字段 ASC/DESC(升序/降序)
LIMIT 起始位置,个数;
*/
#查询出员工的所有信息
SELECT *
FROM t_employee;
#在基础查询之上对年龄进行降序排序
SELECT *
FROM t_employee
ORDER BY age DESC;
#在排序的基础之上，进行分页
SELECT *
FROM t_employee
ORDER BY age DESC
LIMIT 5, 8;#第0个代表第一个 第六个使用的位置是5
#5
#6
``` ```