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This article mainly shows you "what is the common function of MySQL", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "what is the common function of MySQL" this article.

Common functions of MySQL I. numeric functions

Additional: ceil (x) such as ceil (1.23) can be written as ceiling (x) if the value is 2.

Second, string function

Underlining is commonly used (number of bytes)

Additional: char_length character (query name followed by three digits) such as: char_length (name) = 3 can be written as:

Select left (name,1) from C1; III. Time function

Usage: select now ()

IV. System function

To add a delimiter:

Select concat_ws ('#', name,tel,height) from xxb;select (substr (Now (), 1mai 4)-substr (age,1,4) as Age from zxc

The following SQL statement states: the first now () is used for comparison. Interval 50 minute means to push back 50 units.-50 means to push forward 50 units year (now ()) to take the year; month (now ()) to take the month; day (now ()) to take the day; nour (now ()) to take the time; minute (now ()) to take points; second (now ()) to take seconds.

Select now (), date_add (now (), interval 50 minute)

Get week:

Select dayofweek (now ()), dayname (now ()); 5. Aggregate function

Collect multiple data to calculate a single data value.

Usage:

Select sum (heigth) from C1

Take the number of records (the number of rows), filter the null value: count () if 14 lines have a blank line, then count () is 13 lines count () can take count (*) this is more accurate, generally use count (*) to count

Calculate the difference between two dates by multiple units such as: select timestampdiff (time unit, date time 1, date time 2) is written as follows:

Select timestampdiff (day,'2021-11-18)

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