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PHP and MySQL syntax：修訂間差異

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=== timer ===
=== timer ===
Recording the time elapsed after the sql query was executed.
<pre>
<pre>
SELECT @timer := CURRENT_TIMESTAMP();
SELECT @timer := CURRENT_TIMESTAMP();

2016年5月13日 (五) 03:03的版本

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: 2026-09-05 13:46:06 

/* 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');

current timestamp

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

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


yesterday

specified time

convert the unix timestamp to human readable time format

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

/* 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`

convert human-readable time to timestamp

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: 9月 5, 2026 -> 2026-09-5

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 */

date interval

When people said 2026-09-01 ~ 2026-09-03, it means 2026-09-01 00:00:00 ~ 2026-09-03 59:59:59 in the system.

Query by month

mysql ex: find the records in January, 2026<ref>sql - MySQL Query GROUP BY day / month / year - Stack Overflow</ref> 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`) = '2026' AND MONTH(`time`) = '1' /*MONTH(`time`) = '1' or MONTH(`time`) = '01' are both ok*/
  • SELECT * FROM `table_name` WHERE DATE_FORMAT(`time`, '%Y-%m') = '2026-01'
  • SELECT * FROM `table_name` WHERE `time` LIKE '2026-01%' /*find the time records starting with the string 2026-01 */
  • SELECT * FROM `table_name` WHERE DATE(`time`) between '2026-01-01' AND '2026-01-31' https://planetoid.info/images/Icon_exclaim.gif add the DATE function to the `time` field
  • SELECT * FROM `table_name` WHERE `time` >= '2026-01-01 00:00:00' AND `time` < '2026-02-01 00:00:00'
  • SELECT * FROM `table_name` WHERE `time` >= '2026-01-01 00:00:00' AND `time` <= '2026-01-31 59:59:59'

date format

sample output: 2026-09-5

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';

further reading

Math

Format a number

Round a number downward to its nearest integer

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


reload

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

find unique (non duplicated) data

text match

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

if(in_array($var, $array){
//do something
}
  • preg_match...
if($var =="AAA" OR $var =="BBB" OR $var =="CCC"){
//do something
}

text input filter

export/import sql file

export/import sql file


reverse the boolean value

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

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

references

<references/>

取自「https://wiki.planetoid.info/index.php?title=PHP_and_MySQL_syntax&oldid=16673」