This tutorial explains MySQL DROP TABLE statement which deletes the specified tables from the in-use database. We’ll describe several usages of this method with the help of simple examples. 1. DROP TABLE Syntax 2. DROP TABLE If Exist 3. DROP TABLE Matching Pattern 4. DROP TABLE Full Example Let’s now read and understand each of the section one by one. MySQL DROP TABLE statement As stated initially, the DROP TABLE is a built-in MySQL statement which removes a specified table from the database. So, let’s first check the details and see how to use the DROP command. But first, create

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This tutorial explains MySQL ABS() which is a Math/Trig function. It takes a number as input and determines its absolute (positive) value. We’ll describe the usages of this method with the help of simple examples. 1. ABS() Syntax 2. ABS() Simple Examples 3. ABS() for Expression 4. ABS() with Tables Let’s now go through each of the section one by one. MySQL ABS() Function As stated initially, ABS() is a built-in MySQL function which does some math calculation to derive the absolute value of a number. In Maths term, an absolute value represents the length of a number on the

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This tutorial explains MySQL DATE_ADD function which adds up a slice of time (in days/hours, e.g., 1 day or 10 days) to the given date. We’ll describe the complete date arithmetic of this method with the help of simple examples. 1. DATE_ADD() Syntax 2. DATE_ADD() with -ve Interval 3. DATE_ADD() for Invalid Date 4. DATE_ADD() for Auto Adjustment Let’s now go through each of the section one by one. MySQL DATE_ADD() Function As stated initially, DATE_ADD() is a built-in MySQL function which adds the specified no. of days to a given date. So, let’s now see the details and check

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MySQL How do you restore tablespace?

This is not new information but I have not covered it much so addressing it now for those that need it.

If you lose your ibd files... you lose your data. So if you have a copy of one available.. or even if you are syncing from another database you can still import it.  What/how do you lose tablespace?

Here is a simple example to recover tablespace.



mysql> Create database demo;

mysql> use demo;

mysql> CREATE TABLE `demotable` (
    ->   `id` int(11) NOT NULL AUTO_INCREMENT,
    ->   `dts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    ->   PRIMARY KEY (`id`)
    -> ) ENGINE=InnoDB;


Now we store some data...

…

Thanks……Good stuff…..

So I realized I had not made a post about this after this situation that recently came up.

Here is the scenario: A backup was taken at midnight, they used MySQL dumps per database. Then at ten am the next day the database crashed. A series of events happened before I was called in, but they got it up to a version of the database with MyISAM tables and the IBD files missing from the tablespace.

So option 1, restoring from backup would get us to midnight and we would lose hours of data. Option 2, we reimport the 1000's of ibd files and keep everything. Then we had option 3, restore from backup, then apply the binlogs for recent changes.

To make it more interesting, they didn't have all of the ibd files I was told, and I did see some missing. So not sure how that was possible but option 2 became an invalid option. They, of course, wanted the least data loss possible, so we went with option 3.

…

(Image credit: Pixabay).

In my earlier post, I showed how MySQL, since version 8.0.14, has support for LATERAL derived tables. With LATERAL, a JOIN can have a second table – a subquery-based derived table – be defined based on values from columns of the first table, and thus be re-calculated for each row of the first table.…

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What is new with MySQL 8.0 Delayed Replication ?

Delayed Replication – You can deliberately execute transactions later than the master by a specific duration of time , Why you do that and for what ? Consider this, Accidentally someone did a wrong UPDATE / DELETE in the master and the transaction is committed, Now how can DBA rollback the database system to the last known good condition ? This is when we benefit from MySQL delayed slave replication investment. The default replication delay in MySQL is “0” seconds, To delay the slave by N seconds use the CHANGE MASTER TO MASTER_DELAY = N, The transactions received from the master is not executed until N seconds later than it’s commit on the immediate master. We have blogged here how to setup …

In 5.6 and earlier, the format is 190711 18:44:52 (YYmmdd HH:MM:SS) and the time zone is always the system time zone. Hope that helps.

MySQL Roles are becoming more and more popular. Therefor, we receive more and more questions related to them.

First I encourage you to read this previous 2 posts:

• MySQL 8.0 Roles and GraphML
• MySQL 8.0: Listing Roles

In this post, I will share you some queries I find useful when using MySQL Roles.

Listing the Roles

The first query allows you to list the Roles created on your MySQL Server and if they are assigned to users, and how many:

SELECT any_value(User) 'Role Name', 
       IF(any_value(from_user) is NULL,'No', 'Yes') Active,
       count(to_user) 'Assigned  …