SQL – FUNCTIONS

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As you know, a function is a group of instructions combined together to perform a task. There are so many inbuilt functions in SQL to perform many arithmetic tasks. They are,

  1. Aggregate functions
  2. Scalar functions
  3. Group by function
  4. Having function

1. SQL – Aggregate functions:

Aggregate functions are functions which return single output by calculating values from the table / column. Some of aggregate functions are sum(), count(), avg(), min(), max(), first(), last() etc.

2. SQL – Scalar functions:

Scalar functions are functions which return a single output from the given input value. Some of scalar functions are UCASE(), LCASE(), LEN(), ROUND(), LEN(), MID(), FORMAT(), NOW() etc.

3. SQL – Group by() function:

Group by() function is used with SELECT statements to group similar data in result-set.

4. SQL – Having() function:

HAVING() function acts as a filter which is used to specify conditions on aggregate functions in WHERE clause. The main purpose of HAVING() function is, aggregate functions such as SUM(), COUNT(), AVG(), etc. can’t be used in where clause. So, they are used in where clause with the help of HAVING() function.

List of inbuilt functions in SQL:

Please click on each SQL functions below to know more about them and sample SQL queries with output.

1. Aggregate functions
SUM() SQL SUM() function returns the sum of a column. The column should be numeric.
COUNT() SQL COUNT() function returns/counts the number of rows in a query. But, it will not count any null values/column.
AVG() SQL AVG() function returns the average value of a column. The column should be numeric.
MIN() SQL MIN() function returns the minimum or smallest value of a column. The column should be numeric.
MAX() SQL MAX() function returns the maximum or biggest value of a column. The column should be numeric.
FIRST() SQL FIRST() function returns the first value of the given column.
LAST() SQL LAST() function returns the last value of the given column.
2. Scalar functions
LEN() SQL LEN() function returns the total length of the given column.
MID() SQL MID() function extracts the characters from a text field.
ROUND() SQL ROUND() function is used to round a numeric value to the nearest integer or to the number of decimals specified by the user.
LCASE() SQL LCASE() function converts the given column to lowercase.
UCASE() SQL UCASE() function converts the given column to uppercase.
NOW() SQL NOW() function is used to return system’s current date & time.
FORMAT() SQL FORMAT() function is used to format a field/column value how it should be displayed in the output.
SQRT() SQL SQRT() function is used to find square root value of the given number.
RAND() SQL RAND() function is used to generate some random numbers.
CONCAT() SQL CONCAT() function is used to concatenate 2 or more strings and forms a single string.
3. Group by function
GROUP BY() GROUP BY() function is used in conjunction with a SELECT statement and aggregate functions (such as SUM(), AVG(), MAX() etc.), to group similar data in result-set by one or more columns.
4. Having function
Having() HAVING() function in SQL acts as a filter which is used to specify conditions on aggregate functions in WHERE clause. The main purpose of HAVING() function is, aggregate functions such as SUM(), COUNT(), AVG(), etc. can’t be used in where clause. So, they are used in where clause with the help of HAVING() function.

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