Using union in subquery : UNION « Result Set « Oracle PL / SQL

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Oracle PL / SQL » Result Set » UNION 
Using union in subquery
  
SQL>
SQL> CREATE TABLE emp (
  2    emp_id               NUMBER,
  3    ename             VARCHAR2(40),
  4    hire_date        DATE DEFAULT sysdate,
  5    end_date DATE,
  6    rate     NUMBER(5,2),
  7    CONSTRAINT emp_pk    PRIMARY KEY (emp_id)
  8  );

Table created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (101'Mary', to_date('15-Nov-1961','dd-mon-yyyy'),null,169);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (102'Tom', to_date('16-Sep-1964','dd-mon-yyyy'),to_date('5-May-2004','dd-mon-yyyy'),135);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (104'Peter', to_date('29-Dec-1987','dd-mon-yyyy'),to_date('1-Apr-2004','dd-mon-yyyy'),99);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (105'Mike', to_date('15-Jun-2004','dd-mon-yyyy'),null,121);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (107'Less', to_date('2-Jan-2004','dd-mon-yyyy'),null,45);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (108'Park', to_date('1-Mar-1994','dd-mon-yyyy'),to_date('15-Nov-2004','dd-mon-yyyy'),220);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (110'Ink', to_date('4-Apr-2004','dd-mon-yyyy'),to_date('30-Sep-2004','dd-mon-yyyy'),84);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (111'Tike', to_date('23-Aug-1976','dd-mon-yyyy'),null,100);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (112'Inn', to_date('15-Nov-1961','dd-mon-yyyy'),to_date('4-Apr-2004','dd-mon-yyyy'),70);

row created.

SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (113'Kate', to_date('3-Mar-2004','dd-mon-yyyy'),to_date('31-Oct-2004','dd-mon-yyyy'),300);

row created.

SQL>
SQL>
SQL> SET ECHO ON
SQL> SELECT all_dates.emp_date, COUNT(*)
  2  FROM (
  3     SELECT hire_date emp_date
  4     FROM emp
  5     UNION ALL
  6     SELECT end_date
  7     FROM empall_dates
  8  GROUP BY all_dates.emp_date
  9  ORDER BY COUNT(*DESC;
                   4
15-NOV-61          2
04-APR-04          2
02-JAN-04          1
03-MAR-04          1
01-APR-04          1
05-MAY-04          1
15-JUN-04          1
30-SEP-04          1
31-OCT-04          1
15-NOV-04          1
01-MAR-94          1
29-DEC-87          1
23-AUG-76          1
16-SEP-64          1

15 rows selected.

SQL>
SQL>
SQL> drop table emp;

Table dropped.

SQL>

   
    
  
Related examples in the same category
1.Union result set in action
2.union with like operator
3.UNION: adds all rows from the first and the second query, eliminate any duplicates, and return the results
4.A UNION query that uses an ORDER BY clause
5.Combining Data with UNION and subquery
6.Combining Data with UNION for single column
7.Union DBA_TABLES and DBA_INDEXES
8.Union date column
9.Union dba_indexes and dba_tables
10.Union two complex queries and subquery
11.Eliminate the duplication and mimic a UNION operator by appending the DISTINCT operator
12.Take the result of the MULTISET UNION DISTINCT operation and pass it as an argument to the SET operator to eliminate duplicates.
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