INFORMATION_SCHEMA provides access to database metadata.
Metadata is data about the data.
For example, the name of a database or table, the data type of a column, or access privileges.
INFORMATION_SCHEMA is the information database.
Inside INFORMATION_SCHEMA there are several read-only tables.
They are actually views.
It is possible to select INFORMATION_SCHEMA as the default database with a USE statement.
SELECT ... FROM INFORMATION_SCHEMA statement is a more consistent way to provide access to the information provided by the various SHOW statements that.
mysql> CREATE TABLE Employee(
-> id int,
-> first_name VARCHAR(15),
-> last_name VARCHAR(15),
-> start_date DATE,
-> end_date DATE,
-> salary FLOAT(8,2),
-> city VARCHAR(10),
-> description VARCHAR(15)
-> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values (1,'Jason', 'Martin', '19960725', '20060725', 1234.56, 'Toronto', 'Programmer');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(2,'Alison', 'Mathews', '19760321', '19860221', 6661.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.01 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(3,'James', 'Smith', '19781212', '19900315', 6544.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(4,'Celia', 'Rice', '19821024', '19990421', 2344.78, 'Vancouver','Manager');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(5,'Robert', 'Black', '19840115', '19980808', 2334.78, 'Vancouver','Tester');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(6,'Linda', 'Green', '19870730', '19960104', 4322.78,'New York', 'Tester');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(7,'David', 'Larry', '19901231', '19980212', 7897.78,'New York', 'Manager');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)
-> values(8,'James', 'Cat', '19960917', '20020415', 1232.78,'Vancouver', 'Tester');
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from Employee;
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| id | first_name | last_name | start_date | end_date | salary | city | description |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
| 1 | Jason | Martin | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto | Programmer |
| 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester |
| 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester |
| 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager |
| 5 | Robert | Black | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester |
| 6 | Linda | Green | 1987-07-30 | 1996-01-04 | 4322.78 | New York | Tester |
| 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | Manager |
| 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester |
+------+------------+-----------+------------+------------+---------+-----------+-------------+
8 rows in set (0.00 sec)
mysql>
mysql>
mysql>
mysql> SELECT table_name, table_type, engine
-> FROM information_schema.tables;
+---------------------------------------+-------------+--------+
| table_name | table_type | engine |
+---------------------------------------+-------------+--------+
| CHARACTER_SETS | SYSTEM VIEW | MEMORY |
| COLLATIONS | SYSTEM VIEW | MEMORY |
| COLLATION_CHARACTER_SET_APPLICABILITY | SYSTEM VIEW | MEMORY |
| COLUMNS | SYSTEM VIEW | MyISAM |
| COLUMN_PRIVILEGES | SYSTEM VIEW | MEMORY |
| KEY_COLUMN_USAGE | SYSTEM VIEW | MEMORY |
| PROFILING | SYSTEM VIEW | MEMORY |
| ROUTINES | SYSTEM VIEW | MyISAM |
| SCHEMATA | SYSTEM VIEW | MEMORY |
| SCHEMA_PRIVILEGES | SYSTEM VIEW | MEMORY |
| STATISTICS | SYSTEM VIEW | MEMORY |
| TABLES | SYSTEM VIEW | MEMORY |
| TABLE_CONSTRAINTS | SYSTEM VIEW | MEMORY |
| TABLE_PRIVILEGES | SYSTEM VIEW | MEMORY |
| TRIGGERS | SYSTEM VIEW | MyISAM |
| USER_PRIVILEGES | SYSTEM VIEW | MEMORY |
| VIEWS | SYSTEM VIEW | MyISAM |
| columns_priv | BASE TABLE | MyISAM |
| db | BASE TABLE | MyISAM |
| func | BASE TABLE | MyISAM |
| help_category | BASE TABLE | MyISAM |
| help_keyword | BASE TABLE | MyISAM |
| help_relation | BASE TABLE | MyISAM |
| help_topic | BASE TABLE | MyISAM |
| host | BASE TABLE | MyISAM |
| proc | BASE TABLE | MyISAM |
| procs_priv | BASE TABLE | MyISAM |
| tables_priv | BASE TABLE | MyISAM |
| time_zone | BASE TABLE | MyISAM |
| time_zone_leap_second | BASE TABLE | MyISAM |
| time_zone_name | BASE TABLE | MyISAM |
| time_zone_transition | BASE TABLE | MyISAM |
| time_zone_transition_type | BASE TABLE | MyISAM |
| user | BASE TABLE | MyISAM |
| employee | BASE TABLE | MyISAM |
| v | VIEW | NULL |
+---------------------------------------+-------------+--------+
36 rows in set (0.01 sec)
mysql>
mysql>
mysql>
mysql>
mysql>
mysql> drop table Employee;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>