Oracle SQL in 10 Minutes - Asim Abbasi
CH1: SQL Basics | CH2: SQL Operators | CH3: SQL Built-in Functions | CH4: SQL Joins | CH5: UPDATE, INSERT & DELETE Statements | CH6: CREATE, ALTER & DROP Statements | CH7: Constraints | CH8: Linking Tables vs Joining Tables | CH9: SQL Statements for Other Database Objects | CH10: SQL Statements for Database Security
Chapter 4: SQL Joins
Self Join:
A self join is a join of a table to itself. The same table appear twice
after the FROM clause. We have used e1 and e2 as two different aliases
for the same table. It can be visualized by looking at the following
example.
Example:
SELECT e1.ename||' works for '||e2.ename "Result"
FROM emp e1, emp e2
WHERE e1.mgr = e2.empno;
Output:
Result
---------------------
BLAKE works for KING
CLARK works for KING
JONES works for KING
FORD works for JONES
SMITH works for FORD
ALLEN works for BLAKE
WARD works for BLAKE
MARTIN works for BLAKE
SCOTT works for JONES
TURNER works for BLAKE
ADAMS works for SCOTT
JAMES works for BLAKE
MILLER works for CLARK
Chapter 4: SQL Joins
CH1: SQL Basics | CH2:
SQL Operators |
CH3: SQL Built-in Functions | CH4:
SQL Joins | CH5:
UPDATE, INSERT & DELETE Statements |
CH6: CREATE, ALTER & DROP Statements | CH7:
Constraints | CH8:
Linking Tables vs Joining Tables | CH9:
SQL
Statements for Other Database Objects | CH10:
SQL Statements for
Database Security Share with others: