mysql calculation function details

2. Field concatenation
2. Give some examples of mysql functions

2.1 Symbol Processing
2.2 Phase Treatment
2.3 Value Processing

Functions are not as portable as SQL . Code that can run on multiple systems is called portable . Most SQL statements are relatively portable, and when there are differences between SQL implementations, those differences are usually not that difficult to deal with.

However, the portability of functions is not strong. Almost every major DBMS implementation supports functions that other implementations do not, and the differences are sometimes significant. For the sake of code portability, many SQL programmers do not favor the use of special implementation features. Although this is beneficial,

But it is not always good for application performance. Without using these functions, writing some application code would be difficult. Other methods must be utilized to accomplish the work that the DBMS does very efficiently.

If you decide to use functions, you should make sure to comment your code so that later on you (or others) know exactly what the SQL you wrote means.

2. Field concatenation

SELECT CONCAT(vend_name,'(',vend_country,')') as info
from vendors
ORDER BY vend_name

MySQL also supports the following operators:

2. Give some examples of mysql functions

2.1 Symbol Processing

Left() Returns the characters on the left side of a string Length() Returns the length of a string Locate() Finds a substring of a string Lower() Converts a string to lowercase LTrim() Removes spaces on the left side of a string Right() Returns the characters on the right side of a string RTrim() Removes spaces on the right side of a string Soundex() Returns the SOUNDEX value of a string SubString() Returns the characters of a substring Upper() Converts a string to uppercase

2.2 Phase Treatment

AddDate() adds a date (day, week, etc.)
AddTime() adds a time (hour, minute, etc.)
CurDate() Returns the current dateCurTime() Returns the current timeDate() Returns the date portion of a date and timeDateDiff() Calculates the difference between two datesDate_Add() Highly flexible date operation functionDate_Format() Returns a formatted date or time stringDay() Returns the day portion of a dateDayOfWeek() Returns the corresponding day of the week for a dateHour() Returns the hour portion of a timeMinute() Returns the minute portion of a timeMonth() Returns the month portion of a dateNow() Returns the current date and timeSecond() Returns the seconds portion of a timeTime() Returns the hour portion of a date and timeYear() Returns the year portion of a date

2.3 Value Processing

Abs() Returns the absolute value of a numberCos() Returns the cosine of an angleExp() Returns the exponential value of a numberMod() Returns the remainder of a division operationPi() Returns the ratio of piRand() Returns a random numberSin() Returns the sine of an angleSqrt() Returns the square root of a numberTan() Returns the tangent of an angle

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