It is sometimes required to get the result of a stored procedure in a variable which can be used later or to output the result.

To do so, we can use the "OUT" parameter mode while defining stored procedures.

In the below section, we will be writing a stored procedure to get the square root of a number returned in an output variable provided by us.



Stored Procedure Definition:

Store the below stored procedure in a file named my_sqrt.sql and save it.

DELIMITER $$

DROP PROCEDURE IF EXISTS my_sqrt$$

CREATE PROCEDURE my_sqrt(inp_number INT, OUT op_number FLOAT)
BEGIN
    SET op_number=SQRT(inp_number);
…

I’m using Redmine to manage projects and bug reports, I was needing a daily report with spent time by user on each project, nothing complicated, but I wanted a cross-reference result like Excel dynamic tables. As we know, MySQL doesn’t support dynamic cross-reference queries but I make an approach:

1. Write the main query with rows: project identifier, task subject and total hours in a date range.

SELECT p.identifier, 
        e.issue_id, i.subject, round(SUM(e.hours),2) AS total_hours
        FROM redmine_nsp.time_entries e
        INNER JOIN redmine_nsp.issues i ON e.issue_id = i.id
        INNER JOIN redmine_nsp.projects p ON e.project_id = p.id
        WHERE e.spent_on BETWEEN '2014-07-01' AND '2014-07-07'
 GROUP BY p.identifier,e.issue_id;

+------------+----------+----------------------------+-------------+
| identifier | issue_id | subject                    | total_hours | …

If you have been using certain DBMSs, or reading recent versions of the SQL standard, you are probably aware of the so-called “WITH clause” of SQL.
Some call it Subquery Factoring. Others call it Common Table Expression. A form of the WITH CLAUSE, “WITH RECURSIVE”, allows to design a recursive query: a query which repeats itself again and again, each time using the results of the previous iteration. This can be quite useful to produce reports based on hierarchical data. And thus is an alternative to Oracle’s CONNECT BY. MySQL does not natively support WITH RECURSIVE, but it is easy to emulate it with a generic, reusable stored procedure. Read the full article …

[2017 update: MySQL 8.0.1 now features SQL-standard CTE syntax; more information is here ; the entry below, from 2013, shows how to work around the absence of CTEs in older MySQL versions.]

If you have been using certain DBMSs, or reading recent versions of the SQL standard, you are probably aware of the so-called "WITH clause" of SQL.
Some call it Subquery Factoring. Others call it Common Table Expression (CTE). In its simplest form, this feature is a kind of "boosted derived table".

Assume that a table T1 has three columns:

CREATE TABLE T1(
YEAR …

Just recently did the presentation and Q&A for the Using Perl Stored Procedures presentation at Percona Live 2013.

The presentation has been uploaded:

Using Perl Stored Procedures for MariaDB from Antony T Curtis

(repeat posting because planet.mysql.com didn't notice it the first time around)

I discovered a feature (or bug) of MySQL timestamp fields. Maybe is documented in some place what I not read yet:

When I add a new timestamp field to a table, MySQL magically adds some features to new timestamp field like a “trigger” and a default value to CURRENT_TIMESTAMP.

There is test-case script:

-- CREATING TABLE AND INSERT SOME DUMMY DATA
mysql> CREATE TABLE t(
    -> id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    -> val VARCHAR(50)
    -> );
Query OK, 0 ROWS affected (0.15 sec)
 
mysql> INSERT INTO t (val) VALUES ("foo") ,("var");
Query OK, 2 ROWS affected (0.08 sec)
Records: 2  Duplicates: 0  Warnings: 0
 
mysql> SELECT * FROM t;
+----+------+
| id | val  |
+----+------+
|  1 | foo  |
|  2 | var  |
+----+------+
2 ROWS IN SET (0.00 sec)
 
 
-- ADDING NEW TIMESTAMP FIELD AND ADD MORE DUMMY DATA
mysql> ALTER TABLE t ADD ts_field TIMESTAMP;
Query OK, 2 ROWS affected (0.35 sec)
Records: 2  Duplicates: 0 …

I was tired to get manually disk space used for all MySQL databases, I just created a stored procedure to get an overview of the database sizes in our MySQL server.

MySQL don’t have a command that allows us an overall summary of the databases, something like SHOW TABLE STATUS for databases. The “SHOW DATABASES” command lists only the current databases without any other information like how many space are using or how many tables there are, etc.

The procedure that I wrote this based on INFORMATION_SCHEMA database, which contains rich information of all existing databases.

I suggest, in a previous post, place all these procedures in a database called tools, but you can still choose different location.

So when call the procedure will have a global view of information that will be useful for maintenance tasks.

mysql> call tools.sp_overview(); …

I write a fair number of scripts on this site and have posted a lot of code over the years. Generally if I am not pasting the code to be viewed on the webpage then I link to a file that a user can download; which leads to a lot of mish-mash code that doesn’t have a home. I’ve always kept the code files in a private SVN repo over the years but have recently moved them all to BitBucket Git repositories. So here they are: lots of code samples and useful bits of programming to save time.

Generic Shell Scripts: https://bitbucket.org/themattreid/generic-bash-scripts/src
Generic Python Scripts: https://bitbucket.org/themattreid/generic-python-scripts/src
Generic MySQL Stored Procs: …

If you’ve ever been troubleshooting on the MySQL command line and needed to quickly see how much memory is being used then you’ve probably noticed that there are no built in commands to give you this data. Unlike other enterprise databases MySQL doesn’t have a very robust management system built in to help make the DBA’s life easier. It doesn’t come with built in Stored Procedures to report on usage statistics or generate handy reports; so we have to code them and import them to MySQL — no relying on Oracle to help us out here.

So, here’s a stored procedure that can be imported to MySQL and run whenever you need to see the memory usage statistics. Installation and usage info is built into the SP below. The SP can also be downloaded from the repo: https://bitbucket.org/themattreid/generic-sql-scripts/src/15c75632f1af/mysql-memory-report-storedproc.sql

##################################################################### …

Example using a mysql cursor in a stored procedure. Mysql Cursor example DELIMITER $$   DROP PROCEDURE IF EXISTS mysql_cursor_example $$ CREATE PROCEDURE mysql_cursor_example ( IN in_name VARCHAR(255) ) BEGIN -- First we declare all the variables we will need DECLARE l_name VARCHAR(255); -- flag which will be set to true, when cursor reaches end [...]