Introduction and advanced MySQL (13)

---

Exist as a condition at the location of the query condition

A． send ⽤in
Eg1： Check the students who failed the exam ⽣ list
B． send ⽤not in
Eg2： The query is not based on C language ⾔ Understand the learning of software programming exam ⽣ list
– A． Use in
– Eg1： Check the list of students who failed the exam
select studentid from exam where exam<60
select * from studentinfo where studentid in(
select studentid from exam where exam<60
)
– B． Use not in
– Eg2： The query is not based on C List of students for language understanding software programming exam
select * from subject where subjectname=‘ be based on C Language understanding software programming ’
select studentid from exam where subjectid=1
select * from studentinfo where studentid not in(
select studentid from exam where subjectid=(
select subjectid from subject where subjectname=‘ be based on C Language understanding software
Programming ’) )
C． send ⽤all
Eg3： Query results ⽐“C003” this ⻔ Any grade in the course is ⼤ Science ⽣ Test information .
D． send ⽤any
Eg4： Query results ⽐“C003” this ⻔ One of the courses ⼀ Achievements ⾼ Science ⽣ Test information
C． Use all: all >all( Subquery , The return value is multiple rows and one column ),
If the value is greater than all in the sub query results true It should be displayed, otherwise it will not be displayed ：>max Eg3： Query score ratio “ be based on C Language understanding software programming ” Examination information of students whose grades are high in this course .

 select * from `subject` where subjectname=' be based on C Language understanding software programming '
 select * from exam where subjectid=1
 select * from exam where exam>all(
 select exam from exam where subjectid=(
select subjectid from `subject` where subjectname=' be based on C Language understanding software 
 Programming '));
 select * from exam where exam>(
 select max(exam) from exam where subjectid=(
select subjectid from `subject` where subjectname=' be based on C language 
 Understand software programming '))
 -- D． Use any: arbitrarily ,>any( Subquery ) ： Greater than any value in the subquery ,>min
 -- Eg4： Query score ratio “C003” Examination information of a student with high scores in this course 
 select * from exam where exam>any(
 select exam from exam where subjectid=(
select subjectid from `subject` where subjectname=' be based on C Language understanding software 
 Programming ' );
select * from exam where exam>(
select min(exam) from exam where subjectid=(
select subjectid from `subject` where subjectname=' be based on C language 
 Understand software programming ' ) );