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Showing entries 1 to 10 of 18 8 Older Entries

Displaying posts with tag: MySQL / MariaDB (reset)

Send messages between sessions on MySQL or MariaDB
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Suppose you want to send a message from one SQL session to one or more other sessions, like "Hey, session#13, here is the latest figure for your calculation, please acknowledge". I'll say what Oracle and EnterpriseDB and DB2 do, then rate the various ways to implement something similar in MySQL and MariaDB, and finish with a demo of the procedure that we use, which is available as part of an open-source package.

The syntax was established by Oracle, with EnterpriseDB and IBM following suit. The details are in the Oracle 12c manual and the …

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MYSQL_HISTFILE and .mysql_history
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The MySQL manual says:
"mysql Logging
On Unix, the mysql client logs statements executed interactively to a history file. By default, this file is named .mysql_history in your home directory. To specify a different file, set the value of the MYSQL_HISTFILE environment variable."
The trouble with that is: it doesn't tell you what you don't need to know. So I'll tell you.


The history-file concept that MySQL and MariaDB are following is indeed "on Unix" and specifically is like the …

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Connecting to MySQL or MariaDB with sockets on Linux
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The MySQL manual says

--socket=file_name, -S file_name ... On Unix, the name of the Unix socket file to use, for connections made using a named pipe to a local server.
The default Unix socket file name is /tmp/mysql.sock.

which might surprise folks who've had to contend with the error message
"Can't connect to local MySQL server through socket '[something-other-than-/tmp/mysql.sock]'".

I'll try to explain here why the name is often something quite different, how to know what the MySQL server is really …

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The ocelotgui debugger
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I have merged a debugger for MySQL/MariaDB stored procedures and functions into our GUI client and posted the source and binaries on github. It allows breakpoint, clear, continue, next, skip, step, tbreakpoint, and variable displays. Features which are rare or missing in other debuggers include:
its current platform is Linux;
it allows breakpoints on functions which are invoked within SQL statements;
it never changes existing stored procedures or functions;
it is integrated with a general GUI client;
it allows commands like gdb and allows menu items / shortcut keys like ddd; …

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Stored Procedures: critiques and defences
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I've gathered the main critiques of MySQL / MariaDB stored procedures, and will try some defences.


The critique:

SQL/PSM is the standard 4GL and it was the work of Andrew Eisenberg. Andy based it on ADA. Unless you are military, you have never seen ADA. Be grateful it is dead.
-- Joe Celko, reminiscing about his days on the SQL standard committee

Actually I believe Mr Celko likes SQL/PSM, which is the standard that MySQL and MariaDB follow. Here at last is your chance to see some Ada …

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I know of seven DBMSs that support GET DIAGNOSTICS: DB2, Oracle Rdb, MySQL, MariaDB, …

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Temporary tables, standard SQL
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The PostgreSQL manual says:

"The standard's definition of the behavior of temporary tables is widely ignored. PostgreSQL's behavior on this point is similar to that of several other SQL databases."

The first sentence is false. The second sentence could be rephrased as "MySQL copied us", although nobody else did, as far as I know.

The standard's definition is widely followed

I base this claim on the documentation of …

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An open-source MySQL/MariaDB GUI client on Linux
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We've written a GUI application. Its command-line options are like those in the mysql client. Its graphic features are an SQL-statement text editor and a scrollable SQL result set. It runs on Linux now and we believe it could be ported to other platforms.

Here are four screenshots.

The startup is as non-GUI as can be -- in fact it gets options from the command line, or from my.cnf, the same way that the mysql client does. Wherever it seemed reasonable, we asked: What would mysql do?

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The BINARY and VARBINARY data types
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MySQL's support of the BINARY and VARBINARY data type is good, and the BINARY and VARBINARY data types are good things. And now the details. What applies here for MySQL applies for MariaDB as well.

Who supports VARBINARY

There's an SQL:2008 standard optional feature T021 "BINARY and VARBINARY data types". Our book has a bigger description, but here is one that is more up to date:

DBMS Standard-ish? Maximum length
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Roles Review
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A role is a bundle of GRANTed privileges which can be assigned to users or which can take the place of users. When there are hundreds or thousands of users, administration becomes a horrible burden if the DBMS doesn't support roles. Our online ANSI-standard book has syntax descriptions. Other DBMSs do support roles, and MySQL has had a worklog task "WL#988 Roles" for many years. Earlier attempts to implement them included a Google Summer of Code project and …

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Showing entries 1 to 10 of 18 8 Older Entries

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