Nisi's work blog » mysql

How to replace substring in MySQL table field

admin — Fri, 11 Mar 2011 12:30:34 +0000

This replace will search in every row of the table where condition from WHERE is true and replace function will replace all instances in a string.

ex. if you have text “hello world” and you want to replace the “o” letter with “*” this will will transform the text in “hell* w*rld”

UPDATE `mytable`
SET my_content = REPLACE(content, ‘substr_string_to_replace’,‘the_new_string’)
WHERE INSTR(content, ‘substr_string_to_replace’) > 0;

MySQL: Select “last month” records

admin — Fri, 04 Feb 2011 12:27:21 +0000

In order to select last month records you have to get first dai of the last month and the last day of the first month.

Remember that current month could be January and the last month will in another year.

Finding first day of the last month:

DATE_FORMAT(CURRENT_DATE – INTERVAL 1 MONTH, "%Y-%m-01")

Finding the last thay of the last month:

LAST_DAY(CURRENT_DATE – INTERVAL 1 MONTH)

And the final Query is:

SELECT *
FROM `my_table`
`DATE` BETWEEN DATE_FORMAT(CURRENT_DATE – INTERVAL 1 MONTH, "%Y-%m-01") AND LAST_DAY(CURRENT_DATE – INTERVAL 1 MONTH)

MySQL: select “this month” records

admin — Fri, 04 Feb 2011 12:20:18 +0000

Where “date” column is a Date type in “my_table”

SELECT *
FROM `my_table`
WHERE YEAR(`DATE`) = YEAR(CURDATE()) AND MONTH(`DATE`) = MONTH(CURDATE())

MySQL: Select last 7 days records

admin — Fri, 04 Feb 2011 12:14:37 +0000

For this example I use this table model:

ID	Name	Date
1	Jon Dow	2011-01-10
2	Jane Dow	2011-01-10
…	…	…

SELECT *
FROM `my_table`
WHERE `DATE` BETWEEN DATE_ADD(CURDATE(), INTERVAL -5 DAY) AND CURDATE()

MySQL: Select today, yesterday or day before yesterday records

admin — Mon, 10 Jan 2011 09:29:46 +0000

Usualy when you work with records where a date or timestamp field is present you need to select records from:

today records
yesterday records
day before yesterday records

Lets say you have a table (my_table) like this:

ID	Name	Date
1	Jon Dow	2011-01-10
2	Jane Dow	2011-01-10
…	…	…

where `Date` is date type field

Today records:

SELECT *
FROM `my_table`
WHERE `DATE` = CURDATE()

Yesterday records:

SELECT *
FROM `my_table`
WHERE `DATE` > DATE_ADD(CURDATE(), INTERVAL -2 DAY) AND
`DATE` < CURDATE()

Day before yesterday records:

SELECT *
FROM `my_table`
WHERE `DATE` > DATE_ADD(CURDATE(), INTERVAL -3 DAY) AND
`DATE` < DATE_ADD(CURDATE(), INTERVAL -2 DAY)

If your `Date` field is a timestamp or datetime then replace `Date` with date(`Date`)

Neural Networks in PHP

admin — Tue, 09 Mar 2010 10:43:28 +0000

Browsing phpclasses.org I had found a very interesting article Neural Networks in PHP . For anyone who dont know yet “Neural networks allow emulating the behavior of a human brain in software applications.”

In this article you can read how to implement Neural Mesh to develop Neural Network applications in PHP. (Neural Networks in PHP)

Neural Mesh is an open source, pure PHP code based Neural Network manager and framework that makes it easier to work with Neural Networks.

Neural Mesh home page: http://neuralmesh.com/

Pure PHP & MySQl
Adaptive Learning
Implement in any enviroment
Web Api
Fast

Restore MySql database using command line

admin — Thu, 17 Dec 2009 11:55:06 +0000

mysql -u USER -p DBNAME < dump.sql

Where:

USER is your username
DBNAME is Databas witch will be restored
dump.sql (any .sql file can be used) is your database dump

Format PHP Date to MySQL Format

admin — Sat, 17 May 2008 00:07:15 +0000

When you insert or update a date in a mysql Table you have to remember that Mysql have 3 types of date

DATETIME ( default format 0000-00-00 00:00:00 )
DATE ( default format 0000-00-00 )
TIMESTAMP ( default format 0000-00-00 00:00:00 )

PHP code:

DATE -> $mysqldate = date( ‘Y-m-d’ );
DATETIME, TSTAMP -> $mysqldate = date( ‘Y-m-d H:i:s’);

Now maybe you have have read some date field from MySql table and want to convert it to PHP date

$phpdate = strtotime( $mysqldate );

MySQL variables range

admin — Thu, 24 Apr 2008 17:08:43 +0000

TINYINT
A very small integer
The signed range is –128 to 127. The unsigned range is 0 to 255.

SMALLINT
A small integer
The signed range is –32768 to 32767. The unsigned range is 0 to 65535

MEDIUMINT
A medium-size integer
The signed range is –8388608 to 8388607. The unsigned range is 0 to 16777215

INT or INTEGER
A normal-size integer
The signed range is –2147483648 to 2147483647. The unsigned range is 0 to 4294967295

BIGINT
A large integer
The signed range is –9223372036854775808 to 9223372036854775807. The unsigned range is 0 to 18446744073709551615

FLOAT
A small (single-precision) floating-point number. Cannot be unsigned
Ranges are –3.402823466E+38 to –1.175494351E-38, 0 and 1.175494351E-38 to 3.402823466E+38. If the number of Decimals is not set or <= 24 it is a single-precision floating point number

DOUBLE,
DOUBLE PRECISION,
REAL
A normal-size (double-precision) floating-point number. Cannot be unsigned
Ranges are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0 and 2.2250738585072014E-308 to 1.7976931348623157E+308. If the number of Decimals is not set or 25 <= Decimals <= 53 stands for a double-precision floating point number

DECIMAL,
NUMERIC
An unpacked floating-point number. Cannot be unsigned
Behaves like a CHAR column: “unpacked” means the number is stored as a string, using one character for each digit of the value. The decimal point, and, for negative numbers, the ‘-‘ sign is not counted in Length. If Decimals is 0, values will have no decimal point or fractional part. The maximum range of DECIMAL values is the same as for DOUBLE, but the actual range for a given DECIMAL column may be constrained by the choice of Length and Decimals. If Decimals is left out it’s set to 0. If Length is left out it’s set to 10. Note that in MySQL 3.22 the Length includes the sign and the decimal point

DATE
A date
The supported range is ‘1000-01-01’ to ‘9999-12-31’. MySQL displays DATE values in ‘YYYY-MM-DD’ format

DATETIME
A date and time combination
The supported range is ‘1000-01-01 00:00:00’ to ‘9999-12-31 23:59:59’. MySQL displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format

TIMESTAMP
A timestamp
The range is ‘1970-01-01 00:00:00’ to sometime in the year 2037. MySQL displays TIMESTAMP values in YYYYMMDDHHMMSS, YYMMDDHHMMSS, YYYYMMDD or YYMMDD format, depending on whether M is 14 (or missing), 12, 8 or 6, but allows you to assign values to TIMESTAMP columns using either strings or numbers. A TIMESTAMP column is useful for recording the date and time of an INSERT or UPDATE operation because it is automatically set to the date and time of the most recent operation if you don’t give it a value yourself

TIME
A time
The range is ‘-838:59:59’ to ‘838:59:59’. MySQL displays TIME values in ‘HH:MM:SS’ format, but allows you to assign values to TIME columns using either strings or numbers

YEAR
A year in 2- or 4- digit formats (default is 4-digit)
The allowable values are 1901 to 2155, and 0000 in the 4 year format and 1970-2069 if you use the 2 digit format (70-69). MySQL displays YEAR values in YYYY format, but allows you to assign values to YEAR columns using either strings or numbers. (The YEAR type is new in MySQL 3.22.)

CHAR
A fixed-length string that is always right-padded with spaces to the specified length when stored
The range of Length is 1 to 255 characters. Trailing spaces are removed when the value is retrieved. CHAR values are sorted and compared in case-insensitive fashion according to the default character set unless the BINARY keyword is given

VARCHAR
A variable-length string. Note: Trailing spaces are removed when the value is stored (this differs from the ANSI SQL specification)
The range of Length is 1 to 255 characters. VARCHAR values are sorted and compared in case-insensitive fashion unless the BINARY keyword is given

TINYBLOB,
TINYTEXT

A BLOB or TEXT column with a maximum length of 255 (2^8 – 1) characters

BLOB,
TEXT

A BLOB or TEXT column with a maximum length of 65535 (2^16 – 1) characters

MEDIUMBLOB,
MEDIUMTEXT

A BLOB or TEXT column with a maximum length of 16777215 (2^24 – 1) characters

LONGBLOB,
LONGTEXT

A BLOB or TEXT column with a maximum length of 4294967295 (2^32 – 1) characters

ENUM
An enumeration
A string object that can have only one value, chosen from the list of values ‘value1’, ‘value2’, …, or NULL. An ENUM can have a maximum of 65535 distinct values.

SET
A set
A string object that can have zero or more values, each of which must be chosen from the list of values ‘value1’, ‘value2’, … A SET can have a maximum of 64 members