PHP and MySQL syntax

mulitple approaches to completing the same/similar task using PHP, MySQL and Excel

time / timestamp

terms of time format

format \ date	1900/1/1	1970/1/1	2016/1/1
column value of unix timestamp (the number of seconds since 1970/01/01)	-2209075200	0	1451606400
column value of Excel DATEVALUE function (number of days since 1900/1/1)	1	25569	42370

now

human readable time format

Convert unix timestamp (the number of seconds since 1970/01/01) <--> to the human readable time format ex: 2024-04-28 19:03:06

• php: echo date("Y-m-d H:i:s", time() ); //Convert the time stamp of current time to the human readable time format. Ex: return '2024-04-28 19:03:06' server timezone dependent
• mysql: default client timezone is server timezone
  • SELECT NOW(); Returns 2024-04-28 19:03:06 which mapping to DATETIME type
  • SELECT NOW()+0; //2011-04-01 12:19:43 returns 20110401122023.000000
  • SELECT CURRENT_TIMESTAMP; Returns 2024-04-28 19:03:06 Current time zone of MySQL is SYSTEM & client timezone dependent.
  • convert mysql datatype timestamp (UTC) to Taipei datetime (client timezone dependent)

/* approach 1: */
SET time_zone='+8:00';
SELECT CURRENT_TIMESTAMP();

/* approach 2: Detect server timezone automatically! Note the precision of time difference between server timezone to your preferred timezone is hours NOT to minutes */
SELECT convert_tz(
   CURRENT_TIMESTAMP(),   
   CONCAT(
     ROUND(
      TIME_TO_SEC(timediff(now(),convert_tz(now(),@@session.time_zone,'+00:00')))/3600),  ':00')
   , '+08:00');

/* approach 3: If you already know the server timezone ex: -05:00 */
SELECT convert_tz(CURRENT_TIMESTAMP,  '-05:00', '+08:00');

• shell script with GUN date installed in Linux , Mac or Cygwin of Win :
  • echo `date +\%Y-\%m-\%d\ %H:%M:%S` 2>&1 or date +\%Y-\%m-\%d\ %H:%M:%S Returns 2024-04-28 19:03:06 server timezone dependent
  • echo `TZ=Asia/Taipei date +\%Y-\%m-\%d\ %H:%M:%S` 2>&1 or TZ=Asia/Taipei date +\%Y-\%m-\%d\ %H:%M:%S Returns 2024-04-28 19:03:06 force to use Taipei timezone

current timestamp

the number of seconds since 1970/01/01. UTC±0

• php: echo time();
• php: echo microtime(); PHP: microtime - Manual "Returns current Unix timestamp with microseconds" //ex: 0.45920500 1406776901
• mysql: SELECT UNIX_TIMESTAMP(); //ex: 2011-05-30 01:56:38 returns 1306720622
• javascript: getTime() Method ex: new Date().getTime(); //Return the number of milliseconds since 1970/01/01
• EXCEL: Excel date to Unix timestamp - Stack Overflow

compare the timestamp and human readable time format using MySQL

SELECT @@global.time_zone, @@session.time_zone;

SELECT UNIX_TIMESTAMP( ) , FROM_UNIXTIME( UNIX_TIMESTAMP( ) ,  '%Y-%m-%d %H:%i:%S' );
 /* 
 1st column: timezone of UNIX_TIMESTAMP( ) is UTC
 2nd column: 'FROM_UNIXTIME( UNIX_TIMESTAMP( ) ,  '%Y-%m-%d %H:%i:%S' )' is server timezone dependent
 */

today & yesterday

today

• MySQL: SELECT CURRENT_DATE; or SELECT CURDATE(); Returns 2024-04-28
• EXCEL: =TODAY() Returns 2024/04/28
• Shell script in Linux or Mac with GUN date installed.
  • echo $(date +"%Y-%m-%d") or echo `date +\%Y-\%m-\%d` 2>&1 or date +"%Y-%m-%d" Returns 2024-04-28
  • specify timezone: echo $(TZ=":Asia/Taipei" date +"%Y-%m-%d") or echo $(TZ=":US/Eastern" date +"%Y-%m-%d")

yesterday

• MySQL:
• EXCEL:
• PHP:
• Shell script in Linux with GUN date installed. Not work on Mac
  • echo $(date -d "yesterday" '+%Y-%m-%d') //Returns sample: 2024-04-24
  • specify timezone: echo $(TZ=":Asia/Taipei" date -d "yesterday" '+%Y-%m-%d') or echo $(TZ=":US/Eastern" date -d "yesterday" '+%Y-%m-%d')

specified time

convert the unix timestamp to human readable time format

ex: 2010-12-21 10:05:06

• PHP: echo date("Y-m-d H:i:s", 1292897201 ); // Using date() function that converting the time stamp 1292897201 to the human readable time format. similar: gmdate() function [Last visited: 2014-04-30] server timezone dependent
• MySQL:
  • SELECT FROM_UNIXTIME( 1306311155 ); //convert the time stamp 1306311155 to the human readable time format 2011-05-25 08:12:11 server timezone dependent
  • SELECT FROM_UNIXTIME( 1306311155, '%Y-%m-%d %H:%i:%S' ); //convert the time stamp 1306311155 to the human readable time format 2011-05-25 08:12:11 server timezone dependent
  • convert mysql datatype timestamp (UTC) to Taipei datetime (client timezone dependent)

/* approach1 */
SET time_zone='+8:00';
SELECT FROM_UNIXTIME( `column_of_timestamp` ,  '%Y-%m-%d %H:%i:%S' ) FROM `table`;

/* approach2: detect server timezone automatically. Note the precision of time difference between server timezone to your preferred timezone is hours NOT to minutes */
SELECT convert_tz(
   FROM_UNIXTIME( `column_of_timestamp` ,  '%Y-%m-%d %H:%i:%S' ),   
   CONCAT(
     ROUND(
      TIME_TO_SEC(timediff(now(),convert_tz(now(),@@session.time_zone,'+00:00')))/3600),  ':00')
   , '+08:00')
FROM `table`

/*  approach3: If you already know the server timezone ex: -05:00 */
SELECT convert_tz(
   FROM_UNIXTIME( `column_of_timestamp` ,  '%Y-%m-%d %H:%i:%S' ),  '-05:00', '+08:00')
FROM `table`

• Excel
  • =( unix_time_stamp /86400)+DATE(1970,1,1) // convert the unix time stamp 1421539200 to the human readable time format 2015/1/18

convert human-readable time to timestamp

• PHP: using strtotime() function ex: strtotime('2010-12-21 10:05:06')
• mysql:
  • SELECT UNIX_TIMESTAMP('2011-03-15 18:53:57'); /* return timestamp: 1300186437 */ server timezone dependent
  • SELECT UNIX_TIMESTAMP(STR_TO_DATE('2011-03-15 18:53:57', '%Y-%m-%d %H:%i:%S')); /* return timestamp: 1300186437 */ server timezone dependent
• Excel:
  • input data (A2 cell): YYYY/MM/DD (e.g. 2024/04/28 ) or YYYY/MM/DD HH:MM (e.g. 2024/04/28 19:03)
  • =(A2-DATE(1970,1,1))*86400

convert datevalue (number of days since 1900/1/1) ↔ to human-readable date

• Excel: =DATEVALUE(Cell_of_date) // ex: =DATEVALUE("2015/1/27") returns 42031. DATEVALUE of 1900/1/1 is 1
• Excel: =TEXT(Cell_of_datevalue,"yyyy/mm/dd") // ex: =TEXT(42031,"yyyy/mm/dd") returns 2015/1/27

convert month name to numeric date ex: April 28, 2024 -> 2024-04-28

• PHP:
• MySQL: STR_TO_DATE(str,format) ex: SELECT STR_TO_DATE('April 28, 2024','%M %d, %Y');
• Excel

PHP microtime to MySQL timestamp

PHP microtime to MySQL timestamp

time difference of two time values

• php: using mktime() function
• mysql: using TIMEDIFF() function ex: SELECT TIMEDIFF('2016:02:01 00:00:00', '2016:01:01 00:00:00'); /* return 744:00:00 */ time difference between two DATETIME values

timer

Recording the time elapsed after the sql query was executed.

SELECT @timer := CURRENT_TIMESTAMP();
SELECT SLEEP(2); //sleep 2 seconds for testing purpose
SELECT 'custom message' AS 'action', CURRENT_TIMESTAMP() AS 'end time', @timer AS 'start time', TIMEDIFF(CURRENT_TIMESTAMP(), @timer) AS 'time elapsed';

date interval

When people said 2024-04-01 ~ 2024-04-03, it means 2024-04-01 00:00:00 ~ 2024-04-03 59:59:59 in the system.

Query by month

mysql ex: find the records in January, 2024 Data type of column `time` is datetime (ex: yy:mm:dd hh:mm:ss). Using one of sql queries as following. online demo

• SELECT * FROM `table_name` WHERE YEAR(`time`) = '2024' AND MONTH(`time`) = '1' /*MONTH(`time`) = '1' or MONTH(`time`) = '01' are both ok*/
• SELECT * FROM `table_name` WHERE DATE_FORMAT(`time`, '%Y-%m') = '2024-01'
• SELECT * FROM `table_name` WHERE `time` LIKE '2024-01%' /*find the time records starting with the string 2024-01 */
• SELECT * FROM `table_name` WHERE DATE(`time`) between '2024-01-01' AND '2024-01-31' add the DATE function to the `time` field
• SELECT * FROM `table_name` WHERE `time` >= '2024-01-01 00:00:00' AND `time` < '2024-02-01 00:00:00'
• SELECT * FROM `table_name` WHERE `time` >= '2024-01-01 00:00:00' AND `time` <= '2024-01-31 59:59:59'

date format

sample output: 2024-04-28

• Use MySQL DATE() Function: DATE( time )
• Use MySQL DATE_FORMAT() Function: DATE_FORMAT( time, '%Y-%m-%d')

further reading

• PHP Date and Time functions
• MySQL The DATETIME, DATE, and TIMESTAMP Types
• MySQL Date and Time Functions
• PHP Date / Time Functions / PHP Date / Time 函数
• Help:Magic words - MediaWiki

Math

Format a number

• PHP: PHP: number_format - Manual
• MySQL: LPAD(number,3,0) will output 007 if the value of number is 7

Round a number downward to its nearest integer

• PHP: round - Manual
• JavaScript floor() Method
• ROUND 函數 - Excel - Office.com

other

• a >0 OR b > 0 OR c > 0
• a+b+c > 0

trigger to make backup of deleted data before deleting them

MySQL :: Re: before delete trigger to make backup of deleted data

step 1: create table hello_deleted_data with the same structure of table hello

step 2: add a trigger

create trigger hello before delete on hello 
for each row 
insert into hello_deleted_data (x,y,z) 
values (OLD.x, OLD.y, OLD.z); 

tested on version: mysqlnd 5.0.7-dev - 091210

redirect/reload to (another) page

redirect

• HTML: html redirect
• PHP:
  • header() to new location PHP: header - Manual
  • echo HTML redirect
• Javascript
  • Javascript Tutorial - Redirect ex: window.location = "http://www.google.com/"
  • iframe - Changing parent window's URL from IFRAME content - AV5

reload

• Javascript
  • iframe (reload) - parent.location.reload();

find unique (non duplicated) data

• SELECT DISTINCT column FROM table
• (1)SELECT * FROM table; (2)Using PHP: array_unique for data handling two or more columns
• SELECT column FROM table GROUP BY column

text match

• PHP in_array; jQuery.inArray()

//PHP code snippet:
$array = array("AAA", "BBB", "CCC");

if(in_array($var, $array){
//do something
}

• preg_match...

• verbose approach: IF (0 == 'String') always be true?

if($var =="AAA" OR $var =="BBB" OR $var =="CCC"){
//do something
}

text input filter

• PHP: PDO::prepare + PDOStatement::bindParam
• PHP: mysqli::real_escape_string

export/import sql file

export/import sql file

reverse the boolean value

• PHP:

$var = true;
print( !$var); //add ! symbol to reverse the boolean value

• EXCEL: NOT 函數 - Excel ex: =NOT(TRUE) will return FALSE

ideas

filter some records

• approach 1: (1) select * under some condition, (2) collect the $identifiers which matched the condition. and then (3) select some records NOT IN ( $identifiers )
• approach 2: (1) select * and then (2) unset some records which matched the condition.

documentation

How to generate the table schema

1. Using phpMyAdmin or other MySQL client
2. Input the SQL query:

   EXPLAIN table_name;

3. Print view (with full texts)
4. Easy to copy the table to other work processor
5. (optional) Adjust the text size to 10

debug

SQL syntax debug