Summary of commonly used SQL in MySQL operation tables

1. View the types of fields in the table

describe table_name
desc table_name

2. Rename the table

rename table original table name to new table name;

3. Solve the mysql query timeout

select /+QUERY_TIMEOUT(150000000000)/ * from table_name
SQL plus +/+QUERY_TIMEOUT(150000000000)/

4. View the index

show index from table_name

5. Create a normal index

create index index name on table name (field name)
alter table table name add index index name (field name)

6. Create a joint index

alter table table name add index index name (field name 1, field name 2)

7. Create a primary key index

alter table table name add primary key (field name)

8. Delete the index

drop index index_name on table_name
alter table table name drop index index name

9. Create a unique index

create unique index index name on table name (field name);

10. Group by has the function of removing duplicates

11. Try to use SQL to solve problems that can be solved with SQL statements instead of writing code.

12. Delete table operation

drop table if exists stu;

13. Use alter to add fields to the table

ALTER TABLE [table name] ADD [column name] [type]
alter table table1 add transactor varchar(10) not Null;

14. Use alter to delete table fields

ALTER TABLE [table name] DROP [column name]

15. Use alter to modify column names

ALTER TABLE [table name] CHANGE [column name] [new name]

16. Modify the table name

ALTER TABLE tbl_name rename new_tbl_name;

17. Use explain to analyze the SQL statement of the query and check the query efficiency of SQL.

explain select statementdesc select statement

18. When creating a table, be sure to add comments to each field, using the comment 'comment'

19. For MySQL database tables, the query efficiency and speed of the primary key are greater than those of the ordinary index.

20. The index created today will not take effect until tomorrow.

21. Process large amounts of data using partitioning, table sharding, and database sharding operations.

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