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192 lines
2.6 KiB
Markdown
192 lines
2.6 KiB
Markdown
# Essential MySQL Functions
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MySQL has many built-in functions. We will covering some important most used built-in functions; for a complete list refer to the online MySQL Reference Manual (http://dev.mysql.com/doc/).
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> NOTE: As of now we will be going through only function and their output, as they would be self explanatory.
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## Numeric Functions
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```sql
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SELECT ROUND(5.73)
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```
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6
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```sql
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SELECT ROUND(5.73, 1)
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```
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5.7
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```sql
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SELECT TRUNCATE(5.7582, 2)
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```
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5.75
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```sql
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SELECT CEILING(5.2)
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```
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6
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```sql
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SELECT FLOOR(5.7)
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```
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5
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```sql
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SELECT ABS(-5.2)
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```
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5.2
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```sql
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SELECT RAND() -- Generates a random floating point number b/w 0 & 1
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```
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## STRING Functions
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```sql
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SELECT LENGTH('sky')
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```
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3
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```sql
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SELECT UPPER('sky')
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```
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SKY
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```sql
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SELECT LOWER('sky)
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```
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sky
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```sql
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SELECT LTRIM(' sky')
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```
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sky
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```sql
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SELECT RTRIM('sky ')
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```
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sky
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```sql
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SELECT TRIM(' sky ')
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```
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sky
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```sql
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SELECT LEFT('Kindergarten', 4)
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```
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Kind
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```sql
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SELECT RIGHT('Kindergarten', 6)
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```
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garten
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```sql
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SELECT SUBSTRING('Kindergarten', 3, 5)
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```
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nderg
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```sql
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SELECT LOCATE('n','Kindergarten') -- LOCATE returns the first occurrence of a character or character string, if found, otherwise it returns 0
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```
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3
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```sql
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SELECT REPLACE('Kindergarten', 'garten', 'garden')
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```
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Kindergarden
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```sql
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SELECT CONCAT('first', 'last')
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```
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firstlast
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## DATE Functions
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```sql
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SELECT NOW()
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```
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2021-10-21 19:59:47
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```sql
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SELECT CURDATE()
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```
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2021-10-21
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```sql
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SELECT CURTIME()
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```
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20:01:12
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```sql
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SELECT MONTH(NOW())
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```
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10
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```sql
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SELECT YEAR(NOW())
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```
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2021
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```sql
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SELECT HOUR(NOW())
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```
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13
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```sql
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SELECT DAYTIME(NOW())
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```
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Thursday
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## Formatting Dates and Times
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> In MySQL, the default date format is "YYYY-MM-DD", ex: "2025-05-12", MySQL allows developers to format it the way they want. We will discuss some of them.
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```sql
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SELECT DATE_FORMAT(NOW(), '%M %D %Y')
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```
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October 22nd 2021
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```sql
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SELECT DATE_FORMAT(NOW(), '%m %d %y')
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```
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10 22 21
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```sql
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SELECT DATE_FORMAT(NOW(), '%m %D %y')
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```
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10 22nd 21
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```sql
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SELECT TIME_FORMAT(NOW(), '%H %i %p')
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```
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14:11 PM
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## Calculating Dates and Times
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```sql
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SELECT DATE_ADD(NOW(), INTERVAL 1 DAY) --return tomorrows date and time
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```
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2021-10-23 14:26:17
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```sql
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SELECT DATE_ADD(NOW(), INTERVAL -1 YEAR)
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```
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or
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```sql
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SELECT DATE_SUB(NOW(), INTERVAL 1 YEAR)
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```
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> Both the queries will return the same output
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2020-10-22 14:29:47
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```sql
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SELECT DATEDIFF('2021-09-08 09:00', '2021-07-07 17:00') -- It will return the difference in number of days, time won't be considered
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```
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63
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```sql
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SELECT TIME_TO_SEC('09:00') - TIME_TO_SEC('09:02')
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```
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-120
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