Monday, 28 July 2014

Useful Complex Queries in SQL

1. Ordering a result set with a column not in result set or queried tables

Order by a column that is not appear in SELECT clause:
--------------------------------------------------------

SELECT empno, ename, sal, deptno
FROM emp
ORDER BY hiredate;

Order by Expression:
----------------------

SELECT empno, ename, sal,deptno,'2' sortby
FROM emp
UNION 
SELECT empno, ename, sal,deptno,'1' sortby
FROM emp 
ORDER BY sortby;

Order by concatenated columns:
---------------------------------

SELECT first_name||' '||Last_name name, salary, deptno
FROM emp_details
order by name;

Order by column position:
---------------------------

SELECT empno, ename, sal, deptno
FROM emp
ORDER BY 1,2;

2. Find string which is not numeric:
SELECT DISTINCT SALES_ORDER FROM T_TEMPORARY_TABLE_30_6718
WHERE REGEXP_LIKE (SALES_ORDER, '[^[:digit:]]');

3.  Check previous row and make it null if same else new value will remain.
Input Record:
C1           C2           C3           C4           DT_PRV_DT
E1           P1           L1            BA1        4/1/2014
E1           P1           L2            BA1        4/2/2014
E1           P2           L2            BA1        4/3/2014
E1           P2           L2            BA2        4/4/2014
Query:
select * from TEST_DATA order by DT_PRV_DT;
select d.C1,
       decode(c2, prev_c2, null, c2) c2,
       decode(c3, prev_c3, null, c3) c3,
       decode(c4, prev_c4, null, c4) c4,
       DT_PRV_DT
  from (select C1,
               C2,
               LAG(c2) OVER(ORDER BY DT_PRV_DT) prev_c2,
               C3,
               LAG(c3) OVER(ORDER BY DT_PRV_DT) prev_c3,
               C4,
               LAG(c4) OVER(ORDER BY DT_PRV_DT) prev_c4,
               DT_PRV_DT
          from TEST_DATA) d
order by DT_PRV_DT;
Output:
C1           C2           C3           C4           DT_PRV_DT
E1           P1           L1            BA1        4/1/2014
E1                           L2                            4/2/2014
E1           P2                                           4/3/2014
E1                                           BA2        4/4/2014

4. Combine the data and get only the not NULL value for each field.
 Create table temp_shoeb (col1 varchar2(50),col2 varchar2(50),col3 varchar2(50),col4 varchar2(50),col_date date);
                COL1      COL2      COL3      COL4      COL_DATE
                val1                                        val4        2/13/2014
                val11      val22                                      2/6/2014
               val111                   val333   val444   2/18/2014
                select * from temp_shoeb order by col_date;
select *
  from (select LAST_VALUE(d.col1 IGNORE NULLS) OVER(ORDER BY d.col_dateROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS column1,
               LAST_VALUE(d.col2 IGNORE NULLS) OVER(ORDER BY d.col_dateROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS column2,
               LAST_VALUE(d.col3 IGNORE NULLS) OVER(ORDER BY d.col_dateROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS column3,
               LAST_VALUE(d.col4 IGNORE NULLS) OVER(ORDER BY d.col_dateROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS column4
          from (select * from temp_shoeb order by col_date) d)
where rownum = 1;
5. LEAD function to update values based on next column:

SELECT ri.RECORDID,
               ri.EMPLOYEE_ID, 
               ri.EFFECTIVE_FROM,
               NVL(LEAD (EFFECTIVE_FROM,1) OVER (PARTITION BY EMPLOYEE_ID ORDER BY EMPLOYEE_ID , EFFECTIVE_FROM ) -1, TO_DATE('12/31/9999','MM/DD/YYYY'))  AS next_eff_from
        FROM T_EMP_HISTORY ri 
        WHERE ri.RECORDID= 7007  
        ORDER BY ri.EMPLOYEE_ID,ri.EFFECTIVE_FROM, next_eff_from;

6. Returning values in update and insert statement

DECLARE
    id          number;
    first_name  varchar2(30);
    last_name   varchar2(30);
    start_date  varchar2(30);
    end_date    varchar2(30);
    salary      varchar2(30);
    city        varchar2(30);
    description varchar2(30);
 BEGIN

    UPDATE employee
       SET salary = salary + (salary * .025) , start_date=sysdate
     where id = 1 returning id, first_name, last_name, start_date, end_date,
     salary, city, description into id, first_name, last_name,
     start_date, end_date, salary, city, description;

    dbms_output.put_line(id || ' ' || first_name || ' ' || last_name || ' ' ||start_date || ' ' || end_date || ' ' || salary || ' ' || city || ' ' ||description);

  END;

1 comment:

  1. Regards
    Sridevi Koduru (Senior Oracle Apps Trainer Oracleappstechnical.com)
    LinkedIn profile - https://in.linkedin.com/in/sridevi-koduru-9b876a8b
    Please Contact for One to One Online Training on Oracle Apps Technical, Financials, SCM, Oracle Manufacturing, BI Publisher, OAF, ADF, SQL, PL/SQL, D2K at sridevikoduru@oracleappstechnical.com | +91 - 9581017828.

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