# SQL functions Class 12 Informatics Practices Notes And Questions

Refer to SQL functions Class 12 Informatics Practices Notes and Questions below. These revision notes and solved important questions for SQL functions have been prepared as per the latest syllabus for class 12 Informatics Practices issued for current academic year. Students should go through these Class 12 Informatics Practices Notes as they will help them to revise all important concepts prior to their examinations

## SQL functions Class 12 Informatics Practices Notes

Basically, it is a set of SQL statements that accept only input parameters, perform actions and return the result. A function can return an only a single value or a table. Functions are not alternate to sql commands but are used as a part of sql command(generally select command).

Types of Function(System defined)

A scalar function is a function that operates on scalar values — that is, it takes one (or more) input values as arguments directly and returns a value.Maths,text, date functions etc. These functions can be applied over column(s) of a table to perform relevant operation on value of each record.
For e.g. select left(name,4) from student;
Will display 4 left side letters of each row of name field from student table.

An aggregate function is a function that operates on aggregate data — that is, it takes a complete set of data as input and returns a value that is computed from all the values in the set. E.g. max(), min(), count(), sum(), avg().Generally these are used for report preparation & mostly used with group by and having clause.

Mathematical functions –Perform operation over numeric value POWER() – power() returns the value of a number raised to the power of another number. The synonym of power() is pow().
Syntax – pow(m,n)
m        A number which is the base of the exponentiation.
n         A number which is the exponent of the exponentiation.
E.g.
Mysql> select pow(2,3);
Mysql>8
Mysql> select pow(2.37,3.45);
Mysql>19.6282……

Mathematical functions
ROUND() – the round() function returns a number rounded to a certain number of decimal places.
Syntax – ROUND(column_name,decimals) column_name -Required. The field to round.

decimals –Required, Specifies the number of decimals to be returned.

Decimal places position value is rounded to next integer ,if its next right side number is>=5
Default decimal place is 0 position if we not specify

Mathematical functions
MOD() –
The MOD() function returns the remainder of one number divided by another. The following shows the syntax of the MOD() function:
Syntax – MOD(dividend,divisor)
Dividend – is a literal number or a numeric expression to divide.
Divisor- is a literal number or a numeric expression by which to divide the dividend.
E.g.
Mysql> SELECT MOD(11, 3); Mysql>2
Mysql> SELECT MOD(10.5, 3);
Mysql>1.5

Text functions- Perform operation over string values.
UPPER() – UPPER(str)
Returns the string str with all characters changed to uppercase.
mysql> SELECT UPPER(‘Tej’);
-> ‘TEJ’
UCASE(str)-UCASE() is a synonym for UPPER().
LOWER(str)-Returns the string str with all characters changed to lowercase
LCASE(str)
LCASE() is a synonym for LOWER().

Text functions- Perform operation over string values.
SUBSTRING(str,pos) – SUBSTRING(str FROM pos),
SUBSTRING(str,pos,len)- SUBSTRING(str FROM pos FOR len)

The forms without a len argument return a substring from string str starting at position pos. The forms with a len argument return a substring len characters long from string str, starting at position pos. The forms that use FROM are standard SQL syntax. It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning.

mysql> SELECT SUBSTRING(‘practically’,5);
-> ‘tically’
mysql> SELECT SUBSTRING(‘foofarbar’ FROM 4);
-> ‘farbar’
-> ‘ratica’
mysql> SELECT SUBSTRING(‘Aakila’, -3);
-> ‘ila’
mysql> SELECT SUBSTRING(‘Aakila’, -5, 3);
-> ‘aki’
mysql> SELECT SUBSTRING(‘Aakila’ FROM -4 FOR 2);
-> ‘ki’

MID(str,pos,len)
MID(str,pos,len) is a synonym for
SUBSTRING(str,pos,len),substr()

Text functions- Perform operation over string values.
LENGTH(str) – Returns the length of the string str
mysql> SELECT LENGTH(‘text’);
-> 4
LEFT(str,len) – Returns the leftmost len characters from the string str, or NULL if any argument is NULL.
mysql> SELECT LEFT(‘Toolbar’, 4);
-> ‘Tool‘
RIGHT(str,len)-Returns the rightmost len characters from the string str, or NULL if any argument is NULL.
mysql> SELECT RIGHT(‘Toolbar’, 3);
-> ‘bar’
Text functions- Perform operation over string values.
INSTR(str,substr)-Returns the position of the first occurrencee of substring substr in string str.
mysql> SELECT INSTR(‘Toobarbar’, ‘bar’);
-> 4
mysql> SELECT INSTR(‘xbar’, ‘ybar’);
-> 0

Text functions- Perform operation over string values.
LTRIM(str)-Returns the string str with leading space characters removed.
mysql> SELECT LTRIM(‘ Toolbar’);
-> ‘Toolbar‘

RTRIM(str)-Returns the string str with trailing space characters removed.
mysql> SELECT RTRIM(‘Toolbar ‘);
-> ‘Toolbar‘
TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str)– Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given , BOTH is assumed.
mysql> SELECT TRIM(‘ tool ‘);
-> ‘bar’
mysql> SELECT TRIM(LEADING ‘x’ FROM ‘xxxtoolxxx’);
-> ‘toolxxx’
mysql> SELECT TRIM(BOTH ‘x’ FROM ‘xxxtoolxxx’);
-> ‘tool’
mysql> SELECT TRIM(TRAILING ‘xyz’ FROM ‘toolxxx’);
-> ‘tool’

Date functions- Perform operation over date values.

NOW()-Returns the current date and time as a value in ‘YYYY-MM-DD hh:mm:ss’ or YYYYMMDDhhmmss format, depending on whether the function is used in string or numeric context.

mysql> SELECT NOW();
-> ‘2020-04-05 23:50:26’
mysql> SELECT NOW() + 0;
-> 20200415235026.000000
Here +0 means +0 second

DATE(expr)-Extracts the date part of the date or datetime expression expr.
mysql> SELECT DATE(‘2003-12-31 01:02:03’);
-> ‘2003-12-31’

Date functions- Perform operation over date values.
MONTH(date)-Returns the month for date, in the range 1 to 12 for January to December, or 0 for dates such as ‘0000-00-00’ or ‘2008-00-00’ that have a zero month part.
mysql> SELECT MONTH(‘2008-02-03’);
-> 2
MONTHNAME(date)-Returns the full name of the month for date.
mysql> SELECT MONTHNAME(‘2008-02-03’);
-> ‘February‘

Date functions- Perform operation over date values.
YEAR(date)-Returns the year for date, in the range 1000 to 9999, or 0 for the “zero” date.
mysql> SELECT YEAR(‘1987-01-01’);
-> 1987
DAY(date)-Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as ‘0000-00-00’ or ‘2008-00-00’ that have a zero day part.
mysql> SELECT DAYOFMONTH(‘2007-02-03’);
-> 3
DAYNAME(date)-Returns the name of the weekday for date.
mysql> SELECT DAYNAME(‘2007-02-03’);
-> ‘Saturday’

Aggregate Functions & NULL- Perform operation over set of values Consider a table Emp having following records as-
Null values are excluded while (avg)aggregate function is used

SQL Queries                                            Result of query
mysql> Select Sum(Sal) from EMP;              12000
mysql> Select Min(Sal) from EMP;                3500
mysql> Select Max(Sal) from EMP;               4500
mysql> Select Count(Sal) from EMP;                3
mysql> Select Avg(Sal) from EMP;               4000
mysql>  Select Count(*) from EMP;                5