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Displaying posts with tag: sql (reset)
How to execute mysql query from a file in your mysql client terminal?

Being a terminal fan myself, I usually find myself running queries in the mysql client instead of a UI interface as it is much faster. You get to see the results instantaneously.

One thing which is pretty tedious is editing a big query again after once running it as the whole multi-line formatted query now appears on a single line, thus reducing its readability.

But no problems, you can edit your query from a file and run the file from your mysql client terminal as many times as you want with as many edits.

To do so, follow the below steps:

1. Open your terminal and cd into the folder you want to store our sample mysql file. Then save your query in a sample file called my_query.sql

$ cd /path/to/folder
$ vim my_query.sql

Save a sample query like:

SELECT * FROM employees
WHERE type LIKE …

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1 million SQL Queries Per Second: MySQL 5.7 on POWER8

I’ve previously covered MySQL 5.6 on POWER (with patch), MySQL 5.6 Performance on POWER8 (spoiler: new performance record) and MySQL 5.7 on POWER.

Of course, The postings on this site are my own and don’t necessarily represent IBM’s positions, strategies or opinions. Also, these numbers should be considered preliminary, but trust me – I did get them and it’s not April 1st.

From my last post, you saw that with my preliminary patch for MySQL 5.7 to work on POWER, we could easily match the previous record for sysbench point select …

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MariaDB/MySQL: Making ENGINE clause mandatory

I got this idea from a Valerii Kravchuk’s MySQL bug report:

http://bugs.mysql.com/bug.php?id=71978

In theory, I completely agree that MySQL and forks should not allow us to set a default storage engine which cannot be used to create a table. You can see the same with MariaDB’s SEQUENCE. The MySQL & forks philosophy seems to be: ignore your mistakes, so you can repeat them forever. Which can turn a mistype into a major data loss.

Unless you only use InnoDB and your magic powers tell you that this will never change, the ENGINE clause should be mandatory in your MySQL installation. Since there is no clean way to make it mandatory, setting a “weird” storage engine as default seems to be a decent workaround. I don’t like it, but it can prevent human mistakes.

MariaDB [test]> SET SESSION …
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MariaDB storage engines

This is a list of MariaDB storage engines that are not distributed with MySQL. I think that most of them will work with MySQL, but not all – at least CassandraSE doesn’t.

Engine Description Introduced
XtraDB A fully-compatible fork of InnoDB, mantained by Percona Big Bang
Aria A crash-safe …
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Oracle 12c VARCHAR2?

The Oracle Database 12c documentation says you can set the maximum size of a VARCHAR2 to 32,767 bytes. That’s true except when you’re trying to map a large Java string to a VARCHAR2. It fails when the physical size of the Java string is greater than 4,000 bytes with an ORA-01002 or fetch out of sequence error.

SELECT read_text_file('C:\Data\loader\Hobbit1.txt')
*
ERROR at line 1:
ORA-24345: A Truncation or null fetch error occurred
 
ERROR:
ORA-01002: fetch out of sequence

You need to grant privileges before you can test this code. You can grant privileges by connecting as the SYS user of a CDB (or non-multitenant database) or as the ADMIN user of a PDB with the AS SYSDBA clause. Then, you run the following command to grant external file access to the JVM inside Oracle Database 12c:

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Descending indexes in MariaDB

Since the dawn of time, MySQL indexes have a limit: they cannot be descending. Yes, ALTER TABLE and CREATE INDEX can contain the ASC and DESC keywords. It is perfectly legal in MySQL. But this does not mean that descending indexes are created. This is a well-known MySQL feature: when it cannot do something, it just pretends to. Well… someone thinks it is a feature. I think it is a bug (a bug is an unexpected behaviour), but what can we do.

The lack of support for descending indexes is only an issue when we need to create an index in which at least one column is ascending and at least one column is descending. For example, MySQL pretends to understand the following statement, but the resulting index won’t probably help us:

CREATE INDEX my_index ON my_table (my_column ASC, your_column DESC);

An ORDER BY my_column ASC, your_column DESC won’t …

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New! MySQL Utilities release-1.4.2-RC

The MySQL Utilities Team is pleased to announce the latest release candidate (RC) release of MySQL Utilities. This release includes a number of improvements for useabilty, stability, and a few enhancements. A complete list of all improvements can be found in our release_notes.

New Utilities!
We have also included two new utilities.

  • The mysqlrplsync utility was added, which checks data consistency between servers in a replicated setup. 
  • The mysqlrplms utility was added, which provides round-robin multi-source replication (a slave server continually cycles through multiple masters in order to store a consolidated data set).


How Can I Download MySQL Utilities?
You can download MySQL Utilities 1.4.2 from the following link using one of the pre-built …

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Announcing MySQL Connector/Arduino 1.0.2 Beta

I've completed a new release of the Connector/Arduino! The new release contains some major improvements with memory handling.

  • The library has been trimmed to save memory.
    • Static strings moved to PROGMEM strings
    • Unused structures removed (e.g. ok_packet)
    • Moved two more methods to optional compilation
  • The WITH_SELECT is turned *OFF* by default. If you want to use select queries, be sure to uncomment this in the mysql.h file.
  • Added a CHANGES.txt file to track changes between releases.


Memory, What Memory?
If you have used previous versions of the connector in medium to large sketches or have long query strings or even many variables, chances are you have hit the memory limit for your wee Arduino board.

This can manifest itself in a number of ways. Most notably, the sketch may work …

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Book review: Getting started with MariaDB

Getting started with MariaDB, by Daniel Bartholomew, is a good book for people who wants to approach MariaDB without knowing MySQL. While this book covers all basic topics, it provides a vast overview of what MariaDB is and can do. In other words: the text is not just about SQL queries.

The book also mentions topics that are not strictly related to MariaDB, but are important for MariaDB users; for example the importance of phisically securing a server, or how to secure a LAN.

The fundamental topics for a MariaDB newbie are covered: installation, …

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Inner vs. Outer Joins
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