This document provides several useful SQL queries for working with dates, numbers, strings, and generating sequences. Some example queries include generating a sequence of numbers from 1 to 12, getting weekend dates between two input dates, generating random numbers, converting comma separated values to tables, getting the first and last day of the month/year, and calculating time differences in days or seconds.

1. Useful Date, Number and String SQL Queries
Geta sequence ofnumbers(1-12) in a table:
We can generate sequence of numbersusingthe connectbyexpression..We canspecifythe upperlimit
inthe level condition.
SELECT ROWNUMMNTH FROMDUAL CONNECTBY LEVEL <= 12
GetWeekenddatesbetweentwoinput dates:
selectdtdate,to_char(to_date(dt),'DY') day
from(selecttrunc(to_date(:DATE_FROM)) +level - 1dt fromdual
connectby trunc(to_date(:DATE_FROM))+level - 1 <= trunc(to_date(:DATE_TO)))
where to_char(to_date(dt),'DY') in('SAT','SUN')
Generate Random numberin SQL query:
selecttrunc(DBMS_RANDOM.value(100,999)) fromdual
SELECT ROUND(DBMS_RANDOM.VALUE() * 100) + 1 ASrandom_numFROMDUAL
ConvertingComma Separated ValuesintoTable:
The querycan come quite handywhenyouhave commaseparateddatastringthat youneedto convert
intotable sothat you can use otherSQL querieslike IN orNOTIN.
Here we are converting'AA,BB,CC,DD,EE,FF'stringtotable containingAA,BB,CCetc.as eachrow.
Once you have thistable youcan joinitwithothertable to quicklydosome useful stuffs.
WITH csv AS (SELECT 'AA,BB,CC,DD,EE,FF'AScsvdataFROMDUAL)
SELECT REGEXP_SUBSTR (csv.csvdata,'[^,]+',1, LEVEL) pivot_char
FROMDUAL, csv
CONNECTBY REGEXP_SUBSTR (csv.csvdata,'[^,]+',1,LEVEL) IS NOT NULL
WITH DATA AS( SELECT 'word1,word2, word3,word4, word5,word6' str FROM dual)
SELECT TRIM(regexp_substr(str,'[^,]+',1, LEVEL)) str
FROMDATA CONNECTBY instr(str,',',1, LEVEL - 1) > 0
ConvertingNumberinto Word:
SELECT TO_CHAR(TO_DATE (1526, 'j'), 'jsp') FROMDUAL
Getthe first day of the month:
Quicklyreturnsthe firstdayof current month.Insteadof currentmonthyou wantto findfirstdayof
monthwhere a date falls,replace SYSDATEwithany date column/value.
SELECT TRUNC (SYSDATE,'MONTH') "Firstday of current month"FROMDUAL
Getthe last day of the month:
Thisqueryis similartoabove butreturnslastday of current month.
One thingworthnotingisthat it automaticallytakescare of leapyear.
So if youhave 29 daysinFeb,it will return29/2.
If you wantto findthe last dayof a monthotherthan the current month,replace SYSDATEwithanydate

2. column/value.
SELECT TRUNC (LAST_DAY(SYSDATE)) "Lastday of current month"FROMDUAL
Getthe first day of the Year:
Firstday of year isalways1-Jan.This querycan be use instoredprocedure where youquicklywantfirst
day of year forsome calculation.
SELECT TRUNC (SYSDATE,'YEAR') "YearFirst Day"FROM DUAL
Getthe last day of the year:
SELECT ADD_MONTHS(TRUNC (SYSDATE,'YEAR'), 12) - 1 "Year Last Day" FROMDUAL
Getnumber ofdays in current month:
Thisqueryreturnsnumberof days incurrentmonth.You can change SYSDATEwithany date/value to
knownumberof daysin that month.
SELECT CAST(TO_CHAR(LAST_DAY (SYSDATE),'dd') ASINT) number_of_daysFROMDUAL
Getnumber ofdays leftin current month:
Belowquerycalculatesnumberof daysleftincurrentmonth
SELECT SYSDATE,LAST_DAY (SYSDATE) "Last",LAST_DAY (SYSDATE) - SYSDATE "Days left"FROMDUAL
Getnumber ofdays betweentwodates:
Use thisqueryto getdifference betweentwodatesinnumberof days
SELECT TRUNC(sysdate) - TRUNC(e.original_date_of_hire) FROMper_periods_of_service
Display each monthsstart and enddate upto last month of the year:
Thisquerydisplaysstartdate and enddate of eachmonthin currentyear.You mightwantto use thisfor
certaintypesof calculations.
SELECT ADD_MONTHS(TRUNC (SYSDATE,'MONTH'), i) start_date,TRUNC (LAST_DAY(ADD_MONTHS
(SYSDATE,i))) end_date
FROMXMLTABLE ('for$i in 0 toxs:int(D) return$i'
PASSINGXMLELEMENT (d,FLOOR (MONTHS_BETWEEN (ADD_MONTHS(TRUNC (SYSDATE,'YEAR') - 1,
12),SYSDATE)))
COLUMNS i INTEGER PATH '.')
Getnumber ofseconds passedsince today (since 00:00 hr):
SELECT (SYSDATE- TRUNC (SYSDATE)) *24 * 60 * 60 num_of_sec_since_morningFROMDUAL
Getnumber ofseconds lefttoday (till 23:59:59 hr):
SELECT (TRUNC(SYSDATE+1) - SYSDATE) * 24 * 60 * 60 num_of_sec_leftFROMDUAL
GetMonth Namesin a year:
selectto_char(add_months(sysdate,LEVEL),'MON') SEQUENCE,
substr(to_char(add_months(sysdate,LEVEL),'DD-MON-YY','nls_date_language=english'),4,3)
MONTH fromdual

3. CONNECTBY LEVEL <= 12
orderby SEQUENCE ASC
Hope thishelps..
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