SQL

SQL> CREATE SEQUENCE TEST_SEQ_A            START WITH 1            MINVALUE 0            MAXVALUE 1            INCREMENT BY -1            NOCACHE            ORDER            CYCLE ; SQL> Insert ... Read more

Sub-query The inner query execute first, the outer query deprnds on inner query output. Correlated sub-query The outer query execute first, the inner query deprnds on outer query result. A correlated sub-query is where the sub-query part makes reference to values from the outer query. ------------------------------------------------------------------------------------------------------------------------------ SELECT emp1.emp_id, emp1.last_name, emp1.job_id, emp1.department_id from employee emp1 WHERE ... Read more

Use rowid pseudo column. All you have to do is to keep the latest data (i.e. highest ROWID) and remove other duplicated rows. SELECT * FROM table1 a WHERE rowid < (SELECT max(rowid) FROM table1 b WHERE a.column1 = b.column1 AND etc...); OR create table testtt (num number); insert into testtt values(111); insert into testtt ... Read more