Reload MySQL Backup to DB
In case you want to reload your backup, here’s the syntax for it.

mysql -u<dbuserid> -p <dbase_name> < <path/filename>


Sample

mysql -uroot -p wp_dbase < /usr/kwatog/wpdb_20100813.sql


Again, it’s so easy, no?

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DATE ADD (SYSDATE +/-1)

SELECT DATE_ADD(SYSDATE(),INTERVAL 1 DAY);
SELECT DATE_ADD(SYSDATE(),INTERVAL -10 DAY);


ADD_MONTHS

SELECT DATE_ADD(SYSDATE(),INTERVAL 1 MONTH);


TRUNC()

SELECT DATE(SYSDATE());


TO_DATE()

SELECT STR_TO_DATE( '07-08-2010', '%d-%m-%Y' );

TIME DIFFERENCE

SELECT TIMESTAMPDIFF(
SECOND , '2010-01-07 23:50:59', SYSDATE( ) ) /3600 /24 day,
TIMESTAMPDIFF(
SECOND , '2010-01-07 23:50:59', SYSDATE( ) ) /3600 hours,
TIMESTAMPDIFF(
SECOND , '2010-01-07 23:50:59', SYSDATE( ) ) /60 mins,
TIMESTAMPDIFF(
SECOND , '2010-01-07 23:50:59', SYSDATE( ) ) secs,

In the preceding example, I could have just used HOUR, MINUTE, DAY, MONTH or YEAR interval but in real world, I mostly use SECOND for a more accurate results. That’s not to say timestampdiff is not accurate. Maybe because I’m used in how I do it in Oracle.

MONTHS_BETWEEN

SELECT TIMESTAMPDIFF(
MONTH , '2010-01-07', SYSDATE( ) ) no_months


Reference:

http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html

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Syntax


IFNULL(expr1,expr2)


Usage

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. Take note that IFNULL() returns a numeric or string value, depending on the context in which it is used. I haven’t used it for other data types yet but I reckon it would have the same results. That is to return the same data type as that of expr1. Another important thing to remember is that expr1 and expr2 should have the same data type

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Case in point is the alpha-numeric auto-generated code. In Oracle, it’s easy to generate AA123, AA124, AA125, etc., etc. All we have to do is concat the alpha part (AA) and with the nextval of sequence. For MySQL, the alpha part and the numeric part have to be saved in separate fields.

However, Maresa of Microshell has created an alternative solution for it. The article discusses a way to emulate the nextval function in mysql. It a nutshell, they created a table similar to the all_sequences of Oracle. This is where you insert your sequences. Then, create a function named nextval() function which increments and returns value of the sequence.
You can check the procedure here.

It’s pretty neat, actually. It’s an excellent alternative and you can even create similar functions like currval(), prevval(), among others. However, I have some reservations on his approach especially on the issue of concurrency. You see in Oracle, calling the nextval() will increment the value and that’s already persisted (saved) in the sequence table even without saving your query/dml statement. On this approach, other queries accessing the pseudo-nextval will have to wait until your query finishes. Not a good idea.

So for now, I’ll will still have to make do with whatever MySQL is providing. If there’s any consolation, MySQL provides LAST_INSERT_ID() function in case you want to get the latest id inserted. See details here here.

So I’m just hoping that MySQL will implement an equivalent feature in the near future. With the imminent takeover by Oracle, I’m actually hoping that development of MySQL will push through and take a steam. We all know that the development of this widely used open-source database engine has been hampered ever since Sun bought it.

Sequence is a little feature. But little as it seems, it solves a lot of problems and helps improve code development time.

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-bash-3.2$mysqldump -ujhondoe -p mydb_name > mydb_name_backup.sql
password:
-bash-3.2$ zip mydb_name_backup.zip mydb_name_backup.sql


Load MySQL Backup Into Database


-bash-3.2$mysql -ujhondoe mydb_name < mydb_name_backup.sql
password:


Create User in MySQL


mysql> CREATE USER 'jhondoe'@'localhost' IDENTIFIED BY 'mypassword';
mysql> GRANT ALL PRIVILEGES ON mydbname.* TO 'jhondoe'@'localhost' WITH GRANT OPTION;

mysql> CREATE USER 'jhondoe'@'%' IDENTIFIED BY 'mypassword';
mysql> GRANT ALL PRIVILEGES ON mydbname.* TO 'monty'@'%' WITH GRANT OPTION;


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Single Table

RENAME TABLE wp_users TO kwg_users;


multiple tables

RENAME TABLE wp_users TO kwtg_users,
wp_usermeta TO kwtg_usermeta,
wp_site TO kwtg_wpsite,
wp_signups TO kwtg_signups;


This is handy when renaming a whole lot of tables as in the case of WordPress mu where each blog has its own set of tables. If you decide to rename them for security reasons (like you forgot to change the default table prefix during installation), it will be a pain to change them one by one through phpMyAdmin.

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