Querying three tables.

Question

hi,
I am new to sql.
I am trying to write a query to retrive information from 3 tables but it is not working.
I need your help.
Problem:
when i try to retrive data from two tables using equlaity condition it is working fine.
SELECT table1.column1, table2.column2 FROM table1, table2 WHERE table1.column1 = table2.column1;
this is working fine and retriving 1200 rows
when i try to use the same condition for checking three tables its not giving correct output.
SELECT table1.column1, table2.column2 FROM table1, table2, table3 WHERE table1.column1 = table2.column1 AND table1.column1 = table3.column1;
this is also working fine and retriving 2400 rows instead of 1200 rows..
My requirement is to get o/p from somr columns of thre tables but the thing is column1 of three tables should match.
your help is greatly appreciated.

Answer 1

I am using three tables
username col. in dba_users should be equal to username col. in test and
grantee col. in dba_role_privs should be equal to username col. in both test and dba_users
dba_users and dba_role_privs and test tables.
desc dba_users
Name Null? Type
USERNAME NOT NULL VARCHAR2(30)
USER_ID NOT NULL NUMBER
PASSWORD VARCHAR2(30)
ACCOUNT_STATUS NOT NULL VARCHAR2(32)
LOCK_DATE DATE
EXPIRY_DATE DATE
DEFAULT_TABLESPACE NOT NULL VARCHAR2(30)
TEMPORARY_TABLESPACE NOT NULL VARCHAR2(30)
CREATED NOT NULL DATE
PROFILE NOT NULL VARCHAR2(30)
INITIAL_RSRC_CONSUMER_GROUP VARCHAR2(30)
EXTERNAL_NAME VARCHAR2(4000)
desc dba_role_privs
Name Null? Type
GRANTEE VARCHAR2(30)
GRANTED_ROLE NOT NULL VARCHAR2(30)
ADMIN_OPTION VARCHAR2(3)
DEFAULT_ROLE VARCHAR2(3)
desc test
Name Null? Type
USERNAME NOT NULL VARCHAR2(30)
TYPE_ID VARCHAR2(2)
PASSWORD VARCHAR2(30)