SQL Statement Summary "constantly updated"

1: query database dbName how many tables

Select COUNT (*) from information_schema.tables where table_schema= ' dbName ';

2: Merge tables based on a field

Select Id,name,sum (operate) from test group by name;

Execution Result:

3: Use an SQL statement to find out the names of students who have more than one class per course

Select name from table group by name have min (Fenshu) >80

4: Delete the same student redundancy information except auto-numbering

Delete tablename whereAuto NumberingNot in (select min (Auto Numbering) from TableName group bySchool Number,name,Course Number,Course Name,score)

 The student table is as follows :
AutoNumber number name Course number Course name score
1 2005001 Zhang San 0001 Mathematics 69
2 2005002 John Doe 0001 Mathematics 89
3 2005001 Zhang San 0001 math

SQL Statement Summary "constantly updated"