delete from product where sno = 1 Warning: Undefined variable $cno in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_product.php on line 8 Fatal error: Uncaught TypeError: mysqli_query(): Argument #1 ($mysql) must be of type mysqli, null given in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_product.php:8 Stack trace: #0 D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_product.php(8): mysqli_query(NULL, 'delete from pro...') #1 {main} thrown in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_product.php on line 8

数据库中delete from s where SNO = 'S2' delete from spj where SNO = 'S2'出现[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'delete from spj where SNO = 'S2'' at line 2怎么办

这个错误是因为你在 SQL 语句中同时执行了两条语句。在 MySQL 中，一个查询只能执行一条语句。...delete from s where SNO = 'S2'; delete from spj where SNO = 'S2'; 这样应该就不会出现语法错误了。

USE JXGL GO CREATE TRIGGER delete_sc_s ON S INSTEAD OF DELETE AS DECLARE @s_no char(8) SELECT @s_no=sno FROM deleted DELETE FROM SC WHERE sno=@s_no DELETE FROM S WHERE sno=@s_no GO USE JXGL GO怎么调用这个触发器

DELETE FROM S WHERE sno='S13' GO 在这个示例中，删除了 S 表中 sno='S13' 的记录。由于已创建了触发器，因此触发器将自动执行，并删除与该记录相关的 SC 表中的所有记录和 S 表中的记录。请注意，在触发器中...

select Sno,Sname from Student where Sno in(select distinct Sno from SC s1 where not exists(select * from SC s2 where s2.Sno='200215121' and not exists(select * from SC s3 where s1.Sno=s3.Sno and s2.Cno=s3.Cno))

这是一个 SQL 查询语句，目的是查找选修了与学号为200215121的学生选修的课程相同的其他学生的学号和姓名。具体实现为：首先从 SC 表中查出所有选过与学号为200215121的学生选修相同课程的学生学号，然后再从 ...

SELECT DISTINCT sno FROM SC WHERE NOT EXISTS ( SELECT cno FROM SC AS T WHERE T.sno = '20201234567' AND NOT EXISTS( SELECT * FROM SC AS TT WHERE sno = TT.sno AND T.cno = TT.cno) );

这是一个SQL语句，作用是查询出没有和学号为'20201234567'的学生选过相同课程的学号。具体解释如下：首先，内层SELECT语句查询出学号为'20201234567'的学生选过的所有课程号，记为T表。然后，外层SELECT语句...

触发器在学生表中删除学生的同时删除选课表的信息 CREATE TRIGGER students_delete_before BEFORM DELETE ON students FOR EACH ROW BEGIN DELETE FROM sc WHERE Sno=old.Sno; END; 更新选课表信息 CREATE TRIGGER students_update_after AFTER UPDATE ON students FOR EACH ROW BEGIN UPDATE sc SET Sno=new.Sno WHERE Sno=old.Sno; END; 学分录入（成绩大于60） CREATE TRIGGER sc_install_after AFTER UPDATE ON sc FOR EACH ROW BEGIN DECLARE xf SAMLLINT; SELECT Ccredit INTO xf FORM course WHERE Cno=new.Cno; IF new.Grade>=60 THEN UPDATE students SET Scredit+xf WHERE Sno=new.Sno; END IF; END;这段代码找出错误并改正

在第三个触发器中，声明变量的语句中... SELECT Ccredit INTO xf FROM course WHERE Cno=new.Cno; IF new.Grade >= 60 THEN UPDATE students SET Scredit = Scredit + xf WHERE Sno = new.Sno; END IF; END;

找出错误并修改SELECT Sno,Sname,Sbirth,Sdept FROM s WHERE Sno in (SELECT Sno FROM sc WHERE Cno=(SELECT Cno FROM c WHERE Cname='

这个SQL查询看起来试图从s表中选择学生的基本信息（Sno、Sname、Sbirth 和 Sdept），但是嵌套了一个复杂的子查询，可能存在一些错误。以下是可能的问题以及修复建议： 1. **缺少圆括号**：外层的IN子查询似乎...

解释一下select Sname from student where not exists( select * from course where course.Cno in (1,2) and not exists( SELECT * from sc where Sno=student.Sno AND Cno=course.Cno ) )

where course.Cno in (1,2) and not exists( ... ) 这个查询语句是查询所有编号为1或2的课程，并且此课程没有学生选过。如果查询结果为空，则说明有学生选了这个课程。最后，这个查询语句再嵌套在外层查询...

select sname from student where not exists (select * from course where not exists (select * from sc where sno=student.sno and Cno=course.cno));

首先，内层的最里层查询语句是查询选了特定课程的学生号和课程号的记录，其中 sno 和 Cno 分别表示学生号和课程号。外层的第二层查询语句是查询选了所有课程的学生号的记录，即找出选课表中没有未选课程的学生。...

修改下列sql语句使其不需要X,Y,Z代称。SELECT X.Cno,X.Cname,X.TotalPer, COUNT(DISTINCT Y.TotalPer)+1 AS '班级排名', COUNT(DISTINCT Z.TotalPer)+1 AS '年级排名' FROM (SELECT A.,B.CLno,C.Cname FROM Report A,Student B,Course C WHERE A.Sno=B.Sno AND A.Cno=C.Cno ) X LEFT JOIN (SELECT A.,B.CLno,C.Cname FROM Report A,Student B,Course C WHERE A.Sno=B.Sno AND A.Cno=C.Cno ) Y ON X.Cno=Y.Cno AND X.CLno=Y.CLno AND (X.TotalPer < Y.TotalPer OR (X.TotalPer = Y.TotalPer AND X.Sno <> Y.Sno)) LEFT JOIN (SELECT A.*,B.CLno,C.Cname FROM Report A,Student B,Course C WHERE A.Sno=B.Sno AND A.Cno=C.Cno )Z ON X.Cno=Z.Cno AND (X.TotalPer < Z.TotalPer OR (X.TotalPer = Z.TotalPer AND X.Sno <> Z.Sno)) WHERE X.Sno='198328005' AND X.Cno='C007' GROUP BY X.Cno,X.Cname,X.TotalPer ORDER BY X.TotalPer DESC

WHERE Report.Sno = Student.Sno AND Report.Cno = Course.Cno) A LEFT JOIN (SELECT Report.*, Student.CLno, Course.Cname FROM Report, Student, Course WHERE Report.Sno = Student.Sno AND Report.Cno = ...

DELETE FROM course WHERE cno IN(SELECT cno FROM sc WHERE sno IN(SELECT sno FROM student WHERE sdept='计算机工程系'));这段查询代码有没有错误

这段 SQL 查询代码看起来没有...具体来说，它首先在 student 表中查找所有 sdept 为计算机工程系的学生的 sno，然后在 sc 表中查找所有选了这些学生的课程的 cno，最后在 course 表中删除这些课程的记录。

用另一种方法解决select sname from student where not exists (select* from sc where sno=student.sno and cno='1');

SELECT sname FROM student LEFT JOIN sc ON student.sno=sc.sno AND cno='1' WHERE sc.sno IS NULL; 这条SQL语句的思路是先将student表和sc表进行LEFT JOIN，关联条件是学生表的sno等于选课表的sno，并且选课表的...

CREATE VIEW V_SCG AS SELECT Sno,Sname,Cname,Score,Credit from student,grade,course WHERE grade.Sno = student.Sno AND grade.Cno = course.Cno AND Cno = '0001'; 哪里错了

在这个 SQL 查询语句中，FROM 子句中的表 student、grade、course 没有使用 JOIN 操作符链接，而是使用了逗号分隔，这会导致查询结果出现笛卡尔积，即每个表中的每一行都与其他表中的每一行进行组合，从而导致查询...

String sql = "select * from sc where sno = '"+sno+"',cno='"+ cno +"'";帮我找出错误

String sql = "select * from sc where sno = '"+sno+"' and cno='"+ cno +"'"; 此外，还需要注意 SQL 注入攻击的问题。建议使用 PreparedStatement 来防止 SQL 注入攻击，例如： String sql = "select * ...

SELECT SNAME FROM S WHERE Sno NOT IN (SELECT Sno FROM SC WHERE Cno = '002') 改用exist

WHERE SC.Sno = S.Sno AND SC.Cno = '002' ); 这将返回一个结果集，其中包含没有选修编号为 '002' 的课程的学生名字。在这个查询中，使用了 EXISTS 子查询，该子查询返回一个布尔值（即真或假），表示是否存在...

select s.* from student s inner join sc ,course c ,teacher t on sc.SNO =s.SNO and c.CNO =sc.CNO and t.TNO =c.TNO where t.TNAME = '张三' order by sc.SCORE desc limit 1,1 这串sql有什么问题，怎么解决

INNER JOIN sc ON sc.SNO = s.SNO INNER JOIN course c ON c.CNO = sc.CNO INNER JOIN teacher t ON t.TNO = c.TNO WHERE t.TNAME = '张三' ORDER BY sc.SCORE DESC LIMIT 1, 1 修正后的语句将按照正确的语法执行内...

delete from user where sno = 1 Fatal error: Uncaught Error: Call to undefined function mysql_query() in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_user.php:8 Stack trace: #0 {main} thrown in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_user.php on line 8

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delete from user where sno = 1 Fatal error: Uncaught Error: Call to undefined function mysql_query() in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_user.php:8 Stack trace: #0 {main} thrown in D:\apache3\apache3\Apache24\htdocs\baoxian\reduce_user.php on line 8

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数据库中delete from s where SNO = 'S2' delete from spj where SNO = 'S2'出现[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'delete from spj where SNO = 'S2'' at line 2怎么办

USE JXGL GO CREATE TRIGGER delete_sc_s ON S INSTEAD OF DELETE AS DECLARE @s_no char(8) SELECT @s_no=sno FROM deleted DELETE FROM SC WHERE sno=@s_no DELETE FROM S WHERE sno=@s_no GO USE JXGL GO怎么调用这个触发器

select Sno,Sname from Student where Sno in(select distinct Sno from SC s1 where not exists(select * from SC s2 where s2.Sno='200215121' and not exists(select * from SC s3 where s1.Sno=s3.Sno and s2.Cno=s3.Cno))

SELECT DISTINCT sno FROM SC WHERE NOT EXISTS ( SELECT cno FROM SC AS T WHERE T.sno = '20201234567' AND NOT EXISTS( SELECT * FROM SC AS TT WHERE sno = TT.sno AND T.cno = TT.cno) );

找出错误并修改SELECT Sno,Sname,Sbirth,Sdept FROM s WHERE Sno in (SELECT Sno FROM sc WHERE Cno=(SELECT Cno FROM c WHERE Cname='

解释一下select Sname from student where not exists( select * from course where course.Cno in (1,2) and not exists( SELECT * from sc where Sno=student.Sno AND Cno=course.Cno ) )

select sname from student where not exists (select * from course where not exists (select * from sc where sno=student.sno and Cno=course.cno));

DELETE FROM course WHERE cno IN(SELECT cno FROM sc WHERE sno IN(SELECT sno FROM student WHERE sdept='计算机工程系'));这段查询代码有没有错误

用另一种方法解决select sname from student where not exists (select* from sc where sno=student.sno and cno='1');

CREATE VIEW V_SCG AS SELECT Sno,Sname,Cname,Score,Credit from student,grade,course WHERE grade.Sno = student.Sno AND grade.Cno = course.Cno AND Cno = '0001'; 哪里错了

String sql = "select * from sc where sno = '"+sno+"',cno='"+ cno +"'";帮我找出错误

SELECT SNAME FROM S WHERE Sno NOT IN (SELECT Sno FROM SC WHERE Cno = '002') 改用exist

select s.* from student s inner join sc ,course c ,teacher t on sc.SNO =s.SNO and c.CNO =sc.CNO and t.TNO =c.TNO where t.TNAME = '张三' order by sc.SCORE desc limit 1,1 这串sql有什么问题，怎么解决

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