SQL - Wildcard Operators
We have already discussed about the SQL LIKE operator, which is used to compare a value to similar values using the wildcard operators.
SQL supports two wildcard operators in conjunction with the LIKE operator which are explained in detail in the following table.
| Sr.No. | Wildcard & Description |
|---|---|
| 1 |
The percent sign (%)
Matches one or more characters.
Note − MS Access uses the asterisk (*) wildcard character instead of the percent sign (%) wildcard character.
|
| 2 |
The underscore (_)
Matches one character.
Note − MS Access uses a question mark (?) instead of the underscore (_) to match any one character.
|
The percent sign represents zero, one or multiple characters. The underscore represents a single number or a character. These symbols can be used in combinations.
Syntax
The basic syntax of a '%' and a '_' operator is as follows.
SELECT FROM table_name WHERE column LIKE 'XXXX%' or SELECT FROM table_name WHERE column LIKE '%XXXX%' or SELECT FROM table_name WHERE column LIKE 'XXXX_' or SELECT FROM table_name WHERE column LIKE '_XXXX' or SELECT FROM table_name WHERE column LIKE '_XXXX_'
You can combine N number of conditions using the AND or the OR operators. Here, XXXX could be any numeric or string value.
Example
The following table has a number of examples showing the WHERE part having different LIKE clauses with '%' and '_' operators.
| Sr.No. | Statement & Description |
|---|---|
| 1 |
WHERE SALARY LIKE '200%'
Finds any values that start with 200.
|
| 2 |
WHERE SALARY LIKE '%200%'
Finds any values that have 200 in any position.
|
| 3 |
WHERE SALARY LIKE '_00%'
Finds any values that have 00 in the second and third positions.
|
| 4 |
WHERE SALARY LIKE '2_%_%'
Finds any values that start with 2 and are at least 3 characters in length.
|
| 5 |
WHERE SALARY LIKE '%2'
Finds any values that end with 2.
|
| 6 |
WHERE SALARY LIKE '_2%3'
Finds any values that have a 2 in the second position and end with a 3.
|
| 7 |
WHERE SALARY LIKE '2___3'
Finds any values in a five-digit number that start with 2 and end with 3.
|
Let us take a real example, consider the CUSTOMERS table having the following records.
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
The following code block is an example, which would display all the records from the CUSTOMERS table where the SALARY starts with 200.
SQL> SELECT * FROM CUSTOMERS WHERE SALARY LIKE '200%';
This would produce the following result.
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 3 | kaushik | 23 | Kota | 2000.00 | +----+----------+-----+-----------+----------+
SQL - Date Functions
The following table has a list of all the important Date and Time related functions available through SQL. There are various other functions supported by your RDBMS. The given list is based on MySQL RDBMS.
| Sr.No. | Function & Description |
|---|---|
| 1 | ADDDATE()
Adds dates
|
| 2 | ADDTIME()
Adds time
|
| 3 | CONVERT_TZ()
Converts from one timezone to another
|
| 4 | CURDATE()
Returns the current date
|
| 5 | CURRENT_DATE(), CURRENT_DATE
Synonyms for CURDATE()
|
| 6 | CURRENT_TIME(), CURRENT_TIME
Synonyms for CURTIME()
|
| 7 | CURRENT_TIMESTAMP(), CURRENT_TIMESTAMP
Synonyms for NOW()
|
| 8 | CURTIME()
Returns the current time
|
| 9 | DATE_ADD()
Adds two dates
|
| 10 | DATE_FORMAT()
Formats date as specified
|
| 11 | DATE_SUB()
Subtracts two dates
|
| 12 | DATE()
Extracts the date part of a date or datetime expression
|
| 13 | DATEDIFF()
Subtracts two dates
|
| 14 | DAY()
Synonym for DAYOFMONTH()
|
| 15 | DAYNAME()
Returns the name of the weekday
|
| 16 | DAYOFMONTH()
Returns the day of the month (1-31)
|
| 17 | DAYOFWEEK()
Returns the weekday index of the argument
|
| 18 | DAYOFYEAR()
Returns the day of the year (1-366)
|
| 19 | EXTRACT
Extracts part of a date
|
| 20 | FROM_DAYS()
Converts a day number to a date
|
| 21 | FROM_UNIXTIME()
Formats date as a UNIX timestamp
|
| 22 | HOUR()
Extracts the hour
|
| 23 | LAST_DAY
Returns the last day of the month for the argument
|
| 24 | LOCALTIME(), LOCALTIME
Synonym for NOW()
|
| 25 | LOCALTIMESTAMP, LOCALTIMESTAMP()
Synonym for NOW()
|
| 26 | MAKEDATE()
Creates a date from the year and day of year
|
| 27 | MAKETIME
MAKETIME()
|
| 28 | MICROSECOND()
Returns the microseconds from argument
|
| 29 | MINUTE()
Returns the minute from the argument
|
| 30 | MONTH()
Return the month from the date passed
|
| 31 | MONTHNAME()
Returns the name of the month
|
| 32 | NOW()
Returns the current date and time
|
| 33 | PERIOD_ADD()
Adds a period to a year-month
|
| 34 | PERIOD_DIFF()
Returns the number of months between periods
|
| 35 | QUARTER()
Returns the quarter from a date argument
|
| 36 | SEC_TO_TIME()
Converts seconds to 'HH:MM:SS' format
|
| 37 | SECOND()
Returns the second (0-59)
|
| 38 | STR_TO_DATE()
Converts a string to a date
|
| 39 | SUBDATE()
When invoked with three arguments a synonym for DATE_SUB()
|
| 40 | SUBTIME()
Subtracts times
|
| 41 | SYSDATE()
Returns the time at which the function executes
|
| 42 | TIME_FORMAT()
Formats as time
|
| 43 | TIME_TO_SEC()
Returns the argument converted to seconds
|
| 44 | TIME()
Extracts the time portion of the expression passed
|
| 45 | TIMEDIFF()
Subtracts time
|
| 46 | TIMESTAMP()
With a single argument this function returns the date or datetime expression. With two arguments, the sum of the arguments
|
| 47 | TIMESTAMPADD()
Adds an interval to a datetime expression
|
| 48 | TIMESTAMPDIFF()
Subtracts an interval from a datetime expression
|
| 49 | TO_DAYS()
Returns the date argument converted to days
|
| 50 | UNIX_TIMESTAMP()
Returns a UNIX timestamp
|
| 51 | UTC_DATE()
Returns the current UTC date
|
| 52 | UTC_TIME()
Returns the current UTC time
|
| 53 | UTC_TIMESTAMP()
Returns the current UTC date and time
|
| 54 | WEEK()
Returns the week number
|
| 55 | WEEKDAY()
Returns the weekday index
|
| 56 | WEEKOFYEAR()
Returns the calendar week of the date (1-53)
|
| 57 | YEAR()
Returns the year
|
| 58 | YEARWEEK()
Returns the year and week
|
ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days)
When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD().
mysql> SELECT DATE_ADD('1998-01-02', INTERVAL 31 DAY); +---------------------------------------------------------+ | DATE_ADD('1998-01-02', INTERVAL 31 DAY) | +---------------------------------------------------------+ | 1998-02-02 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT ADDDATE('1998-01-02', INTERVAL 31 DAY); +---------------------------------------------------------+ | ADDDATE('1998-01-02', INTERVAL 31 DAY) | +---------------------------------------------------------+ | 1998-02-02 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
When invoked with the days form of the second argument, MySQL treats it as an integer number of days to be added to expr.
mysql> SELECT ADDDATE('1998-01-02', 31); +---------------------------------------------------------+ | DATE_ADD('1998-01-02', INTERVAL 31 DAY) | +---------------------------------------------------------+ | 1998-02-02 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
ADDTIME(expr1,expr2)
ADDTIME() adds expr2 to expr1 and returns the result. The expr1 is a time or datetime expression, while the expr2 is a time expression.
mysql> SELECT ADDTIME('1997-12-31 23:59:59.999999','1 1:1:1.000002'); +---------------------------------------------------------+ | DATE_ADD('1997-12-31 23:59:59.999999','1 1:1:1.000002') | +---------------------------------------------------------+ | 1998-01-02 01:01:01.000001 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
CONVERT_TZ(dt,from_tz,to_tz)
This converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value. This function returns NULL if the arguments are invalid.
mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET'); +---------------------------------------------------------+ | CONVERT_TZ('2004-01-01 12:00:00','GMT','MET') | +---------------------------------------------------------+ | 2004-01-01 13:00:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','+00:00','+10:00'); +---------------------------------------------------------+ | CONVERT_TZ('2004-01-01 12:00:00','+00:00','+10:00') | +---------------------------------------------------------+ | 2004-01-01 22:00:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
CURDATE()
Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or in a numeric context.
mysql> SELECT CURDATE(); +---------------------------------------------------------+ | CURDATE() | +---------------------------------------------------------+ | 1997-12-15 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT CURDATE() + 0; +---------------------------------------------------------+ | CURDATE() + 0 | +---------------------------------------------------------+ | 19971215 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
CURRENT_DATE and CURRENT_DATE()
CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE()
CURTIME()
Returns the current time as a value in 'HH:MM:SS' or HHMMSS format, depending on whether the function is used in a string or in a numeric context. The value is expressed in the current time zone.
mysql> SELECT CURTIME(); +---------------------------------------------------------+ | CURTIME() | +---------------------------------------------------------+ | 23:50:26 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT CURTIME() + 0; +---------------------------------------------------------+ | CURTIME() + 0 | +---------------------------------------------------------+ | 235026 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
CURRENT_TIME and CURRENT_TIME()
CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().
CURRENT_TIMESTAMP and CURRENT_TIMESTAMP()
CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW().
DATE(expr)
Extracts the date part of the date or datetime expression expr.
mysql> SELECT DATE('2003-12-31 01:02:03'); +---------------------------------------------------------+ | DATE('2003-12-31 01:02:03') | +---------------------------------------------------------+ | 2003-12-31 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DATEDIFF(expr1,expr2)
DATEDIFF() returns expr1 . expr2 expressed as a value in days from one date to the other. Both expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.
mysql> SELECT DATEDIFF('1997-12-31 23:59:59','1997-12-30'); +---------------------------------------------------------+ | DATEDIFF('1997-12-31 23:59:59','1997-12-30') | +---------------------------------------------------------+ | 1 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DATE_ADD(date,INTERVAL expr unit), DATE_SUB(date,INTERVAL expr unit)
These functions perform date arithmetic. The date is a DATETIME or DATE value specifying the starting date. The expr is an expression specifying the interval value to be added or subtracted from the starting date. The expr is a string; it may start with a '-' for negative intervals.
A unit is a keyword indicating the units in which the expression should be interpreted.
The INTERVAL keyword and the unit specifier are not case sensitive.
The following table shows the expected form of the expr argument for each unit value.
| unit Value | Expected exprFormat |
|---|---|
| MICROSECOND | MICROSECONDS |
| SECOND | SECONDS |
| MINUTE | MINUTES |
| HOUR | HOURS |
| DAY | DAYS |
| WEEK | WEEKS |
| MONTH | MONTHS |
| QUARTER | QUARTERS |
| YEAR | YEARS |
| SECOND_MICROSECOND | 'SECONDS.MICROSECONDS' |
| MINUTE_MICROSECOND | 'MINUTES.MICROSECONDS' |
| MINUTE_SECOND | 'MINUTES:SECONDS' |
| HOUR_MICROSECOND | 'HOURS.MICROSECONDS' |
| HOUR_SECOND | 'HOURS:MINUTES:SECONDS' |
| HOUR_MINUTE | 'HOURS:MINUTES' |
| DAY_MICROSECOND | 'DAYS.MICROSECONDS' |
| DAY_SECOND | 'DAYS HOURS:MINUTES:SECONDS' |
| DAY_MINUTE | 'DAYS HOURS:MINUTES' |
| DAY_HOUR | 'DAYS HOURS' |
| YEAR_MONTH | 'YEARS-MONTHS' |
The values QUARTER and WEEK are available from the MySQL 5.0.0. version.
mysql> SELECT DATE_ADD('1997-12-31 23:59:59', -> INTERVAL '1:1' MINUTE_SECOND); +---------------------------------------------------------+ | DATE_ADD('1997-12-31 23:59:59', INTERVAL... | +---------------------------------------------------------+ | 1998-01-01 00:01:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT DATE_ADD('1999-01-01', INTERVAL 1 HOUR); +---------------------------------------------------------+ | DATE_ADD('1999-01-01', INTERVAL 1 HOUR) | +---------------------------------------------------------+ | 1999-01-01 01:00:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DATE_FORMAT(date,format)
This command formats the date value as per the format string.
The following specifiers may be used in the format string. The '%' character is required before the format specifier characters.
| Sr.No. | Specifier & Description |
|---|---|
| 1 |
%a
Abbreviated weekday name (Sun..Sat)
|
| 2 |
%b
Abbreviated month name (Jan..Dec)
|
| 3 |
%c
Month, numeric (0..12)
|
| 4 |
%D
Day of the month with English suffix (0th, 1st, 2nd, 3rd, .)
|
| 5 |
%d
Day of the month, numeric (00..31)
|
| 6 |
%e
Day of the month, numeric (0..31)
|
| 7 |
%f
Microseconds (000000..999999)
|
| 8 |
%H
Hour (00..23)
|
| 9 |
%h
Hour (01..12)
|
| 10 |
%I
Hour (01..12)
|
| 11 |
%i
Minutes, numeric (00..59)
|
| 12 |
%j
Day of year (001..366)
|
| 13 |
%k
Hour (0..23)
|
| 14 |
%l
Hour (1..12)
|
| 15 |
%M
Month name (January..December)
|
| 16 |
%m
Month, numeric (00..12)
|
| 17 |
%p
AM or PM
|
| 18 |
%r
Time, 12-hour (hh:mm:ss followed by AM or PM)
|
| 19 |
%S
Seconds (00..59)
|
| 20 |
%s
Seconds (00..59)
|
| 21 |
%T
Time, 24-hour (hh:mm:ss)
|
| 22 |
%U
Week (00..53), where Sunday is the first day of the week
|
| 23 |
%u
Week (00..53), where Monday is the first day of the week
|
| 24 |
%V
Week (01..53), where Sunday is the first day of the week; used with %X
|
| 25 |
%v
Week (01..53), where Monday is the first day of the week; used with %x
|
| 26 |
%W
Weekday name (Sunday..Saturday)
|
| 27 |
%w
Day of the week (0=Sunday..6=Saturday)
|
| 28 |
%X
Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
|
| 29 |
%x
Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v
|
| 30 |
%Y
Year, numeric, four digits
|
| 31 |
%y
Year, numeric (two digits)
|
| 32 |
%%
A literal .%. character
|
| 33 |
%x
x, for any.x. not listed above
|
mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00', '%W %M %Y'); +---------------------------------------------------------+ | DATE_FORMAT('1997-10-04 22:23:00', '%W %M %Y') | +---------------------------------------------------------+ | Saturday October 1997 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00' -> '%H %k %I %r %T %S %w'); +---------------------------------------------------------+ | DATE_FORMAT('1997-10-04 22:23:00....... | +---------------------------------------------------------+ | 22 22 10 10:23:00 PM 22:23:00 00 6 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DATE_SUB(date,INTERVAL expr unit)
This is similar to the DATE_ADD() function.
DAY(date)
The DAY() is a synonym for the DAYOFMONTH() function.
DAYNAME(date)
Returns the name of the weekday for date.
mysql> SELECT DAYNAME('1998-02-05'); +---------------------------------------------------------+ | DAYNAME('1998-02-05') | +---------------------------------------------------------+ | Thursday | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DAYOFMONTH(date)
Returns the day of the month for date, in the range 0 to 31.
mysql> SELECT DAYOFMONTH('1998-02-03'); +---------------------------------------------------------+ | DAYOFMONTH('1998-02-03') | +---------------------------------------------------------+ | 3 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DAYOFWEEK(date)
Returns the weekday index for date (1 = Sunday, 2 = Monday, ., 7 = Saturday). These index values correspond to the ODBC standard.
mysql> SELECT DAYOFWEEK('1998-02-03'); +---------------------------------------------------------+ |DAYOFWEEK('1998-02-03') | +---------------------------------------------------------+ | 3 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
DAYOFYEAR(date)
Returns the day of the year for date, in the range 1 to 366.
mysql> SELECT DAYOFYEAR('1998-02-03'); +---------------------------------------------------------+ | DAYOFYEAR('1998-02-03') | +---------------------------------------------------------+ | 34 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
EXTRACT(unit FROM date)
The EXTRACT() function uses the same kinds of unit specifiers as DATE_ADD() or DATE_SUB(), but extracts parts from the date rather than performing date arithmetic.
mysql> SELECT EXTRACT(YEAR FROM '1999-07-02'); +---------------------------------------------------------+ | EXTRACT(YEAR FROM '1999-07-02') | +---------------------------------------------------------+ | 1999 | +---------------------------------------------------------+ 1 row in set (0.00 sec) mysql> SELECT EXTRACT(YEAR_MONTH FROM '1999-07-02 01:02:03'); +---------------------------------------------------------+ | EXTRACT(YEAR_MONTH FROM '1999-07-02 01:02:03') | +---------------------------------------------------------+ | 199907 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
FROM_DAYS(N)
Given a day number N, returns a DATE value.
mysql> SELECT FROM_DAYS(729669); +---------------------------------------------------------+ | FROM_DAYS(729669) | +---------------------------------------------------------+ | 1997-10-07 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
Note − Use FROM_DAYS() with caution on old dates. It is not intended for use with values that precede the advent of the Gregorian calendar (1582).
FROM_UNIXTIME(unix_timestamp)
FROM_UNIXTIME(unix_timestamp,format)
Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or in a numeric context. The value is expressed in the current time zone. The unix_timestamp argument is an internal timestamp values, which are produced by the UNIX_TIMESTAMP() function.
If the format is given, the result is formatted according to the format string, which is used in the same way as is listed in the entry for the DATE_FORMAT() function.
mysql> SELECT FROM_UNIXTIME(875996580); +---------------------------------------------------------+ | FROM_UNIXTIME(875996580) | +---------------------------------------------------------+ | 1997-10-04 22:23:00 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
HOUR(time)
Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23.
mysql> SELECT HOUR('10:05:03'); +---------------------------------------------------------+ | HOUR('10:05:03') | +---------------------------------------------------------+ | 10 | +---------------------------------------------------------+ 1 row in set (0.00 sec)
