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To get some starting number of characters from the data stored in the MySQL table’s column, we can use MySQL LEFT() function. It will return the number of characters specified as its argument. We need to provide the name of the column, having the particular record from which we want to get starting characters, as its first argument. To demonstrate it we are taking the example of a table named ‘examination_btech’ having the following examination details of students −mysql> Select * from examination_btech; +-----------+----------+--------+ | RollNo | Name | Course | +-----------+----------+--------+ | 201712001 | Rahul ... Read More
We can see only the list of stored procedures in a particular MySQL database by the following query −mysql> SELECT ROUTINE_TYPE, ROUTINE_NAME FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_SCHEMA = 'query'AND ROUTINE_TYPE = 'PROCEDURE'// +--------------+------------------------+ | ROUTINE_TYPE | ROUTINE_NAME | +--------------+------------------------+ | PROCEDURE | allrecords | +--------------+------------------------+ 1 row in set (0.05 sec)
As we know that the SUM() function returns NULL if there is no matching row but sometimes we want it to return zero instead of NULL. For this purpose, we can use the MySQL COALESCE() function which accepts two arguments and returns the second argument if the first argument is NULL, otherwise, it returns the first argument. To understand the above concept, consider an ‘employee_tbl’ table, which is having the following records −mysql> SELECT * FROM employee_tbl; +------+------+------------+--------------------+ | id | name | work_date | daily_typing_pages | +------+------+------------+--------------------+ | 1 | John | 2007-01-24 | ... Read More
There are numerous advantages and disadvantages of using MySQL stored procedures which are as follows −MySQL Stored Procedure AdvantagesFollowings are the advantages of using MySQL Stored Procedures −Increasing the performance of applications − As we know that after creating the stored procedure it is compiled and stored in the database. But MySQL implements stored procedures slightly different which helps in increasing the performance of the applications. MySQL stored procedures are compiled on demand. After compiling a stored procedure, MySQL puts it into a cache. And MySQL maintains its own stored procedure cache for every single connection. If an application uses ... Read More
We can write the following query to see only the name and types of procedures in a particular MySQL database. To make it understand we are using the database named ‘query’ −mysql> Select Name, Type from mysql.proc where db = 'query'; +------------+-----------+ | Name | Type | +------------+-----------+ | allrecords | PROCEDURE | | Hello | FUNCTION | +------------+-----------+ 2 rows in set (0.18 sec)
To get some last number of characters from the data stored in MySQL table’s column, we can use MySQL RIGHT() function. It will return the number of characters specified as it argument. We need to provide the name of the column, having the particular record from which we want to get last characters, as its first argument. To demonstrate it we are taking the example of a table named ‘examination_btech’ having the following examination details of students −mysql> Select * from examination_btech; +-----------+----------+--------+ | RollNo | Name | Course | +-----------+----------+--------+ | 201712001 | Rahul | ... Read More
We can see only the list of stored procedures in a particular MySQL database by the following query −mysql> SHOW PROCEDURE STATUS WHERE db = 'query'\G *************************** 1. row *************************** Db: query Name: allrecords Type: PROCEDURE Definer: root@localhost Modified: 2017-11-11 09:56:11 Created: 2017-11-11 09:56:11 Security_type: DEFINER Comment: character_set_client: cp850 collation_connection: cp850_general_ci Database Collation: latin1_swedish_ci 1 row in set (0.01 sec)
When we use MySQL COUNT() function to count the values stored in a column which also stored some NULL values then MySQL ignores the NULL and returns the result for only non-NULL values. To understand it, we are using the data, as follows, from table ‘Employee’ −mysql> Select * from Employee; +----+--------+--------+ | ID | Name | Salary | +----+--------+--------+ | 1 | Gaurav | 50000 | | 2 | Rahul | 20000 | | 3 | Advik | 25000 | | 4 | Aarav | 65000 | | 5 | Ram | 20000 | | 6 | ... Read More
With the help of SHOW TABLES command, we can get only the name having no other information about the tables. For example, we can see the list of tables in a database named tutorial as follows −mysql> show tables; +--------------------+ | Tables_in_tutorial | +--------------------+ | student | +--------------------+ 1 row in set (0.00 sec)
For calculating the sum of only dissimilar values of the column we can use ‘DISTINCT’ keyword along with the name of the column. To understand SUM() function for dissimilar values, consider an ‘employee_tbl’ table, which is having the following records −mysql> SELECT * FROM employee_tbl; +------+------+------------+--------------------+ | id | name | work_date | daily_typing_pages | +------+------+------------+--------------------+ | 1 | John | 2007-01-24 | 250 | | 2 | Ram | 2007-05-27 | 220 | | 3 | Jack | 2007-05-06 | 170 ... Read More