MySQL Articles - Page 368 of 439

As we know the EXPLAIN statement will provide the information/structure of the whole table. With the help of the EXPLAIN statement along with the table name and the column name, we can get the information about that column.SyntaxEXPLAIN table_name col_name;Example1mysql> EXPLAIN employee ID; +-------+---------+------+-----+---------+----------------+ | Field | Type    | Null | Key | Default | Extra          | +-------+---------+------+-----+---------+----------------+ | ID    | int(11) | NO   | PRI | NULL    | auto_increment | +-------+---------+------+-----+---------+----------------+ 1 row in set (0.11 sec)The query above will give the information about the column ‘ID’ of a table named ... Read More

With the statement SHOW FULL COLUMNS, we can get more information about the columns of a table than the information we got by DESCRIBE, EXPLAIN, and SHOW COLUMNS MySQL statements.SyntaxSHOW FULL COLUMNS from Table_name;Examplemysql> SHOW FULL COLUMNS FROM EMPLOYEE\G; *************************** 1. row ***************************      Field: ID       Type: int(11)  Collation: NULL       Null: NO        Key: PRI    Default: NULL      Extra: auto_increment Privileges: select, insert, update, references    Comment: *************************** 2. row ***************************      Field: Name       Type: varchar(20)  Collation: latin1_swedish_ci       Null: YES ... Read More

Followings are the synonyms statements of MySQL DESCRIBE i.e. the statements with the help of which we can get the same kind of information/structure of the table as we get from DESCRIBE −EXPLAIN StatementEXPLAIN is the synonym of the DESCRIBE statement. Its syntax is also similar to the DESCRIBE statement. Consider the following example −mysql> Explain Employee; +-------+-------------+------+-----+---------+------------------+ | Field | Type        | Null | Key | Default | Extra            | +-------+-------------+------+-----+---------+------------------+ | ID    | int(11)     | NO   | PRI | NULL    | auto_increment   | | ... Read More

Subqueries can work well in a SELECT statement FROM clause. Following is the syntax for the same −SELECT … FROM(subquery) [AS] name …To make it understand we are using the following data from table ‘cars’ −mysql> Select * from Cars; +------+--------------+---------+ | ID   | Name         | Price   | +------+--------------+---------+ | 1    | Nexa         | 750000  | | 2    | Maruti Swift | 450000  | | 3    | BMW          | 4450000 | | 4    | VOLVO        | 2250000 | | ... Read More

A subquery that contains a reference to a table that also appears in the outer query is called a correlated subquery. In this case,  MySQL evaluates from inner query to the outer query. To understand it we are having the following data from table ‘cars’ −mysql> Select * from Cars; +------+--------------+---------+ | ID   | Name         | Price   | +------+--------------+---------+ | 1    | Nexa         | 750000  | | 2    | Maruti Swift | 450000  | | 3    | BMW          | 4450000 | | 4 ... Read More

The subquery can return at most one value. The value can be the result of an arithmetic expression or a column function. MySQL then compares the value that results from the subquery with the value on the other side of the comparison operator. MySQL subquery can be used before or after any of the comparison operators like =, >, >=,

As we know that DESCRIBE statement will provide the information/structure of the whole table. With the help of DESCRIBE statement along with table name and the column name, we can get the information about that column.SyntaxDESCRIBE table_name col_name;Example1mysql> Describe employee ID; +-------+---------+------+-----+---------+----------------+ | Field | Type    | Null | Key | Default | Extra          | +-------+---------+------+-----+---------+----------------+ | ID    | int(11) | NO   | PRI | NULL    | auto_increment | +-------+---------+------+-----+---------+----------------+ 1 row in set (0.11 sec)The query above will give the information about the column ‘ID’ of a table named ‘employee’.Example2mysql> Describe ... Read More

The DESCRIBE statement gives information about MySQL table’s structure.ExampleConsider the constructing of the following table name ‘Employee’ with Create Table statement as follows −mysql> Create table Employee(ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT, Name Varchar(20)); Query OK, 0 rows affected (0.20 sec)Now with the help of ‘DESCRIBE Employee‘ statement, we can get the information about the employee table.mysql> Describe Employee; +-------+-------------+------+-----+---------+------------------+ | Field | Type        | Null | Key | Default | Extra            | +-------+-------------+------+-----+---------+------------------+ | ID    | int(11)     | NO   | PRI | NULL    | auto_increment ... Read More

The default sort order in MySQL tables is ascending. Whenever we use ORDER BY clause to sort out the rows of a table, MySQL gives output in ascending order, with the smallest value first. Consider the following example from a table named ‘student’ −mysql> Select * from student order by name; +--------+--------+--------+ | Name   | RollNo | Grade  | +--------+--------+--------+ | Aarav  | 150    | M.SC   | | Aryan  | 165    | M.tech | | Gaurav | 100    | B.tech | +--------+--------+--------+ 3 rows in set (0.00 sec)We can see the query above gives the output, ordered by name, in ascending order, start with smallest value ‘Name’ column.

It can be understood with the help of an example in which we would copy the values of a table into other table. We are using the data from table ‘cars’ and copy its data to table ‘copy_cars’ −mysql> CREATE TABLE copy_cars LIKE cars; Query OK, 0 rows affected (0.86 sec) mysql> SELECT * from copy_cars; Empty set (0.08 sec)The following query using the subquery will insert the values same as ‘cars’ to table ‘copy_cars’ −mysql> INSERT INTO Copy_cars Select * from Cars; Query OK, 8 rows affected (0.07 sec) mysql> SELECT * from copy_cars; +------+--------------+---------+ | ID ... Read More