Structured query language functions

STRUCTURED QUERY
LANGUAGE
FUNCTIONS IN MYSQL

FUNCTIONS IN MYSQL
There are two types of functions in MySQL:
Single Row Functions : Single row functions operate on a single value to
return a single value. They return only one result per row. They are further
categorized into:
Numeric functions
String functions Date
Time functions
Multiple Row Functions: Multiple row functions operate on a set of rows to
return a single value. Examples include SUM(), AVG() and COUNT().

TABLE: ITEM
Consider the table ITEM:
Itemno Name Price Quantity DOP
A001 Bread 20.25 10 2015-05-21
A002 Butter 50.75 6 2015-06-12
A003 Biscuits 10.32 20 2015-12-23
A004 Eggs 70.75 10 2015-09-18
A005 Chocolate 100.35 20 2015-10-19

NUMERIC FUNCIONS
Numeric functions perform operations on numeric values and return numeric values. There are
three numeric functions which are available:
POWER(X,Y) OR POW(X,Y): It returns the value of X raised to the power of Y.
COMMAND OUTPUT EXPLANATION
SELECT POW(2,3) ; 8 2 X 2 X 2 =8
SELECT POW(2, -2); 0.25 1/22 = ¼ = 0.25
SELECT POW(-2,2); 4 -2 X -2 = 4
SELECT POW (-2,3); -8 -2 X -2 X -2 = -8
SELECT ITEMNO,
POW(PRICE,2) FROM ITEM;

ROUND FUNCTION
 ROUND(X,D) function is used to round the value of argument X upto D decimal places.
 If number of decimal places is not specified or is zero, the number rounds to the nearest integer OR 0
decimal places.
 If negative value is specified for precision, it counts off that value left from the decimal point. If positive
value is specified for precision, it counts off that value right from the decimal point.
COMMAND RESULT EXPLNATION
SELECT ROUND(-4.45); -4 No. after decimal is less than 5
SELECT ROUND(-4.67); -5 No. after decimal is more than 5
SELECT ROUND(4.45); 4 No. after decimal is less than 5
SELECT ROUND(4.678,1); 4.7 No. at second place after decimal is more than 5
SELECT ROUND(4.678,0); 5 No. after decimal is more than 5
SELECT ROUND(56.345, -1); 60
SELECT ITEMNO, ROUND(PRICE) FROM
ITEM;

TRUNCATE FUNCTION
 TRUNCATE(X,D) or TRUNC(X,D) returns the number X, truncated to D decimal places.
 If D is 0, the result has no decimal point or fractional part.
 If D is negative, it causes D digits left of the decimal point of the value X to become zero.
COMMAND OUTPUT
SELECT TRUNC(5.678,0); 5
SELECT TRUNC(3.768,1); 3.7
SELECT TRUNC(-9.87,1); -9.8
SELECT TRUNC(345, -2); 300
SELECT ITEMNO,TRUNC(PRICE,1)
ITEM;

STRING(CHARACTER) FUNCTION
String functions operate on character type data. They return either character or numeric
values.
LENGTH(str): Returns the length of the string str.
COMMAND OUTPUT
SELECT LENGTH(“COMPUTER”); 8
SELECT LENGTH(“ I AM LEARNING”); 13
SELECT ITEMNO, LENGTH(NAME) FROM
ITEM;

CONCAT FUNCTION
CONCAT(str1, str2,...) : Returns the string that results from concatenating the arguments.
COMMAND OUTPUT
SELECT CONCAT(“My”,
“SQL”, “CLASS”);
MySQLCLASS
SELECT CONCAT(“My”,
“SQL”,NULL, “CLASS”);
NULL
SELECT CONCAT(ITEMNO,
NAME), PRICE FROM ITEM;
CONCAT(Itemno, Name)
A001Bread
A002Butter
A003Biscuits
A004Eggs
A005Chocolate

INSTR FUNCTION
INSTR(str, substr) : Returns the position of the first occurrence of substring substr in
string str
COMMAND RESUL
T
EXPLANATION
SELECT INSTR(“My SQL”,
“SQL);
4 First match found
at 4th position
SELECT INSTR(“My SQL”,
“SQR”);
0 No match found
SELECT INSTR(NAME,
“BREAD”) FROM ITEM;
INSTR(NAME,”BREAD
”)
1
0
0
0
0

LOWER FUNCTION
LOWER(str) or LCASE(str): Returns the string str in lowercase.
COMMAND RESULT
SELECT
LOWER(“INFORMATICS”)
informatics
SELECT LOWER(NAME)
FROM EMP;
LOWER(Name)
bread
butter
biscuits
eggs
chocolate

UPPER FUNCTION
UPPER(str) or UCASE(str): Returns the string str in lowercase.
COMMAND RESULT
SELECT
UPPER(“INforMAtiCS”);
INFORMATICS
SELECT UPPER(NAME)
FROM EMP;
UPPER(Name)
BREAD
BUTTER
BISCUITS
EGGS
CHOCOLATE

LEFT FUNCTION
LEFT(str, N) : Returns the N characters from the left side of the string str.
COMMAND RESULT
SELECT LEFT(“My SQL”, 2); My
SELECT LEFT(NAME, 3) FROM ITEM;
LEFT(Name, 3)
Bre
But
Bis
Egg
Cho

RIGHT FUNCTION
RIGHT(str, N) : Returns the N characters from the right side of the string str.
COMMAND RESULT
SELECT RIGHT(“My SQL”, 3); SQL
SELECT RIGHT(NAME, 3) FROM ITEM;
RIGHT(Name)
ead
ter
its
ggs
ate

LTRIM FUNCTION
LTRIM(str) : Returns the leading spaces ie from the left side of the string str.
COMMAND RESULT
SELECT LTRIM(“
INFORMATICS”);
INFORMATICS
SELECT LTRIM(NAME)
FROM EMP;
LTRIM(Name)
Bread
Butter
Biscuits
Eggs
Chocolate

RTRIM FUNCTION
RTRIM(str) : Removes the trailing spaces ie from the right side of the string str.
COMMAND RESULT
SELECT RTRIM(“INFORMATICS
”);
INFORMATICS
SELECT RTRIM(NAME) FROM
EMP;
RTRIM(Name)
Bread
Butter
Biscuits
Eggs
Chocolate

TRIM FUNCTION
TRIM(str) : Removes both leading and trailing spaces from the string str .
COMMAND OUTPUT
SELECT TRIM(“ INFORMATICS
PRACTICES ”);
INFORMATICS
SELECT TRIM(NAME) FROM EMP;
TRIM(Name)
Bread
Butter
Biscuits
Eggs
Chocolate

SUBSTRING/SUBSTR/MID FUNCTION
SUBSTRING(str, M,N) or MID(str, M,N): Returns the specified number of characters from
the middle of the string. There are 3 arguments.
 The first argument is the source string.
 The second argument is the position of first character to be displayed.
 The third argument is the number of characters to be displayed.
If the third argument is missing, then starting from the position specified, the rest of the
string is returned.
If the second argument is negative, then the beginning of the substring is M characters
from the end of the string.

SUBSTRING/SUBSTR/MID FUNCTION Contd…
COMMAND OUTPUT
SELECT SUBSTR(“WORLD OF COMPUTERS”, 4 ); or
SELECT SUBSTR(“WORLD OF COMPUTERS” FROM 4 );
LD OF COMPUTERS
SELECT SUBSTR(“WORLD OF COMPUTERS” , 3, 4 ); LD O
SELECT SUBSTR(“WORLD OF COMPUTERS”, -4 ); TERS
SELECT SUBSTR(“WORLD OF COMPUTERS”, -6,3 ); PUT
SELECT SUBSTR(“WORLD OF COMPUTERS” FROM -4
FOR 2 );
TE
SELECT SUBSTR(NAME,2,3) FROM ITEM;
SUBSTR(Nam
e,2,3)
rea
utt
isc
ggs
hoc

ASCII FUNCTION
ASCII(str): Returns the ASCII value of the leftmost character of the string str.
 Returns 0 if str is an empty string.
 Returns NULL if str is NULL.
COMMAND RESUL
T
EXPLANATION
SELECT ASCII(‘2’); 50 ASCII value of ‘0’ is 48, ‘1’ is 49 , ‘2’ is 50 and so on
SELECT ASCII(‘CG’); 67 ASCII value of ‘A’ is 65, ‘B’ is 66, ‘C’ is 67 and so on
SELECT ASCII(‘are’); 97 ASCII value of ‘a’ is 97, ‘b’ is 98 and so on

DATE AND TIME FUNCTION
COMMAND EXPLANATION EXAMPLE RESULT
CURDATE() Returns the current date in YYYY-
MM-DD format
SELECT CURDATE(); 2015-10-14
NOW() Returns the current date and time in
'YYYY-MM-DD HH:MM:SS'
SELECT NOW(); 2015-10-14 20:10:30
SYSDATE() Returns the current date and time in
'YYYY-MM-DD HH:MM:SS
SELECT SYSDATE(); 2015-10-14 20:10:30
DATE(exp) Extracts the date part of a date or
date time expression
SELECT DATE(‘2015-10-14
20:10:30’);
2015-10-14
MONTH(date) Returns the numeric month from the
date passed, in the range 0 to 12
SELECT MONTH(‘2015-10-
14’);
SELECT MONTH(DOP)
FROM ITEM;
10

DATE AND TIME FUNCTION Contd……
COMMAND EXPLANATION EXAMPLE RESULT
YEAR(date) Returns the year for date passed in
the range 0 to 9999
SELECT YEAR (‘2015-10-14’);
SELECT YEAR(DAP) FROM ITEM;
2015
DAYNAME(da
te)
returns the name of the weekday for
the date passed
SELECT DAYNAME(2015-10-14);
SELECT DAYNAME(DAP) FROM ITEM;
MONDAY
DAYOFMONT
H(date)
Returns the day of the month in the
range 0 to 31.
SELECT DAYOFMONTH(2015-10-14);
SELECT DAYOFMONTH(DAP) FROM
ITEM;
DAYOFWEEK(
date)
Returns the day of week in number
1 for Sunday, 2 for Monday and so
SELECT DAYOFWEEK(2015-10-14);
SELECT DAYOFWEEK(DAP) FROM
ITEM;
DAYOFYEAR(
ate)
Return the day of the year for the
given date in numeric format in the
range 1 to 366.
SELECT DAYOFYEAR(2015-10-14);
SELECT DAYOFYEAR(DAP) FROM ITEM;

SYSDATE() vs NOW()
SYSDATE() returns the time at which the function executes.
While NOW() which returns a constant time that indicates the
time at which the statement began to execute.

Structured query language functions

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