SELECT * FROM tableA, tableB WHERE Conditions [+] - sql

Question

I have the following query
SELECT *
FROM tableA, tableB
WHERE Conditions [+]
What does this keyword Conditions[+] Stands for?
How this query behaves as a outer join?

Answer 1

That is old Oracle Join syntax.
SELECT *
FROM tableA, tableB
WHERE Conditions [+] -- this should be tableA (+) = tableB
The positioning of the + sign denotes the JOIN syntax.
If you query was:
SELECT *
FROM tableA, tableB
WHERE tableA.id (+) = tableB.Id
Then it would be showing a RIGHT OUTER JOIN so the equivalent is:
SELECT *
FROM tableA
RIGHT OUTER JOIN tableB
ON tableB.id = tableA.Id
If the + sign was on the other side then it would be a LEFT OUTER JOIN
SELECT *
FROM tableA, tableB
WHERE tableA.id = tableB.Id (+)
is equivalent to
SELECT *
FROM tableA
LEFT OUTER JOIN tableB
ON tableA.id = tableB.Id
I would advise using standard join syntax though.
If you do not specify a + sign then it will be interpreted as an INNER JOIN
SELECT *
FROM tableA, tableB
WHERE tableA = tableB
it's equivalent is:
SELECT *
FROM tableA
INNER JOIN tableB
ON tableA.id = tableB.id
A FULL OUTER JOIN would be written using two SELECT statements and a UNION:
SELECT *
FROM tableA, tableB
WHERE tableA.id = tableB.Id (+)
UNION
SELECT *
FROM tableA, tableB
WHERE tableA.id (+) = tableB.Id
It's equivalent is:
SELECT *
FROM tableA
FULL OUTER JOIN tableB
ON tableA.id = tableB.id
Here is a tutorial that explains a lot of these:
Old Outer Join Syntax

Answer 2

It is not important how that behaves. You should use the standard syntax for outer joins:
select *
from tableA left outer join
tableB
on . . .
The "(+)" syntax was introduced by Oracle before the standard syntax, and it is highly out of date.

Answer 3

'Conditions' here just means what you're using to filter all this data.
LIke here's an example:
SELECT *
FROM tableA, tableB
WHERE Name like '%Bob%'
would return names that have "Bob" anywhere inside.
About outer joins, actually you'd use that in the FROM clause:
So maybe
SELECT *
FROM tableA ta
OUTER JOIN tableB tb
ON ta.name = tb.name
WHERE ta.age <> 10
and there where here is optional, by the way

Answer 4

I hate to just copy & paste an answer, but this sort of thing can be found pretty easily if you do a little searching...
An outer join returns rows for one table, even when there are no
matching rows in the other. You specify an outer join in Oracle by
placing a plus sign (+) in parentheses following the column names from
the optional table in your WHERE clause. For example:
SELECT ut.table_name, uc.constraint_name
FROM user_tables ut, user_constraints uc
WHERE ut.table_name = uc.table_name(+);
The (+) after uc.table_name makes the user_constraint table optional.
The query returns all tables, and where there are no corresponding
constraint records, Oracle supplies a null in the constraint name
column.