2. SQL--Query table, CREATE TABLE, insert data into table

(1): Query whether a table exists in a database ( two ways): Assuming that the table name is table_name

if exists (select * from sysobjects where name= ' table_name ')
DROP TABLE table_name

If OBJECT_ID (' table_name ') is NOT null
DROP TABLE table_name

The same operation can also be used to determine whether the database exists!

(2): Some instances of the table operation:

create an instance of a table: (Student score table:grade_table)

if exists (select * from sysobjects where name = ' grade_table ')
drop table Grade_table

Go
CREATE TABLE Grade_table
(
Stuid varchar (20),
CourseID varchar (20),
Grade int
)

(3): Insert data in table: (Student score table:grade_table)

INSERT into grade_table values (' 10001 ', ' 001 ', ' 85 ')

INSERT into grade_table values (' 10002 ', ' 001 ', ' 95 ')

(4): update the data in the table:

Update grade_table set grade=70 where stuid= ' 10001 ' and courseid= ' 001 '

(5): Delete data from table:

Delete grade_table where stuid= ' 10001 ' and courseid= ' 001 '

(6): Create a new table with the same student_table as the student and then insert the data queried in student_table, which is generally used to guide some data

  CREATE TABLE student_table
      (
              stuid varchar,
              CourseID varchar,
              grade int
     )
     
      CREATE TABLE Student
      (
              stuid varchar,
              CourseID varchar,
              grade int
     )
     
       INSERT into student_table values (' 10001 ', ' 001 ', ' I ')

INSERT into student_table values (' 10002 ', ' 001 ', ' 95 ')

INSERT INTO student
SELECT * from student_table as S1
where S1.stuid not in (select Stuid from student)

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2. SQL--Query table, CREATE TABLE, insert data into table