Basic Operations of Tables in MySQL Learning Notes

Create table

create table table name

create table if not exists table name

mysql> create database company;
Query OK, 1 row affected (0.00 sec)
mysql> use company;
Database changed
mysql> create table if not exists t_dept(
  -> deptno int,
  -> dname varchar(20),
  -> loc varchar(40));
Query OK, 0 rows affected (0.20 sec)
mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| t_dept      |
+-------------------+
1 row in set (0.00 sec)
mysql>

Display all tables in the current database

show tables;

mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| t_dept      |
+-------------------+
1 row in set (0.00 sec)

View table structure

describe table name

Abbreviation

desc table name

mysql> describe t_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> desc t_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

View table details

show create table table name

mysql> show create table t_dept;
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                            |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t_dept | CREATE TABLE `t_dept` (
 `deptno` int(11) DEFAULT NULL,
 `dname` varchar(20) DEFAULT NULL,
 `loc` varchar(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+--------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
show create table t_dept \G
mysql> show create table t_dept \G
*************************** 1. row ***************************
    Table: t_dept
Create Table: CREATE TABLE `t_dept` (
 `deptno` int(11) DEFAULT NULL,
 `dname` varchar(20) DEFAULT NULL,
 `loc` varchar(40) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

Delete table

drop table table name
drop table if exists table name

mysql> drop table if exists t_dept;
Query OK, 0 rows affected (0.12 sec)
mysql> show tables;
Empty set (0.00 sec)

Modify table name

ALTER TABLE old_table_name RENAME [TO] new_table_name
old_table_name Original table name
new_table_name New table name
Rename t_dept to tab_dept

mysql> alter table t_dept rename tab_dept;
Query OK, 0 rows affected (0.09 sec)
mysql> show tables;
+-------------------+
| Tables_in_company |
+-------------------+
| tab_dept |
+-------------------+
1 row in set (0.00 sec)
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

Add a field to the table, default at the end
ALTER TABLE table_name ADD attribute_name attribute_type

Add a field descri varchar( to tab_dept20)

mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> alter table tab_dept add descri varchar(20);
Query OK, 0 rows affected (0.33 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | varchar(20) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

Add a field at the first position in the table

ALTER TABLE table_name ADD attribute_name attribute_type first

mysql> alter table tab_dept add id int first;
Query OK, 0 rows affected (0.38 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | varchar(20) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Add a field after the specified field in the table

ALTER TABLE table_name ADD attribute_name attribute_type AFTER attribute_name

mysql> alter table tab_dept add comm varchar(20) after dname;
Query OK, 0 rows affected (0.31 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| comm | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | varchar(20) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

Delete field

ALTER TABLE table_name DROP attribute_name

mysql> alter table tab_dept drop comm;
Query OK, 0 rows affected (0.32 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | varchar(20) | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Field modification-Modify field data type
ALTER TABLE table_name MODIFY attribute_name data_type

mysql> alter table tab_dept modify descri int;
Query OK, 0 rows affected (0.45 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Field modification-Modify field name

ALTER TABLE table_name CHANGE old_attribute_name new_attribute_name old_data_type

mysql> alter table tab_dept change id deptid int;
Query OK, 0 rows affected (0.07 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptid | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Field modification-Modify both field name and data type at the same time

ALTER TABLE table_name CHANGE old_attribute_name new_attribute_name new_data_type

mysql> alter table tab_dept change deptid id varchar(32);
Query OK, 0 rows affected (0.49 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | varchar(32) | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Modify order

ALTER TABLE table_name MODIFY attribute_name1 Data type FIRST|AFTER attribute name2

2properties must exist
Move deptno to the first position

mysql> alter table tab_dept modify deptno int first;
Query OK, 0 rows affected (0.33 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| id   | varchar(32) | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

Move ID to the end

mysql> alter table tab_dept modify deptno int after descri;
Query OK, 0 rows affected (0.29 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id   | varchar(32) | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
| deptno | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
mysql> alter table tab_dept modify deptno int first;
Query OK, 0 rows affected (0.34 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table tab_dept modify id int after descri;
Query OK, 0 rows affected (0.47 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc tab_dept;
+--------+-------------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| deptno | int(11)   | YES |   | NULL  |    |
| dname | varchar(20) | YES |   | NULL  |    |
| loc  | varchar(40) | YES |   | NULL  |    |
| descri | int(11)   | YES |   | NULL  |    |
| id   | int(11)   | YES |   | NULL  |    |
+--------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)