Oracle筛选器查询不起作用

Question

I have a query as follows-

Select t1.colmn1, t2.colm1 from table1 t1, table2 t2
where t1.pid = t2.pid
and t1.colm2 is null; --- This query retuns 100 rows

pid column from table 1 has some null values (say 10 records with pid = null). I want to modify above query as it should return these null value rows as well. Like all the 100 records from above query plus 10 records having pid = null.

I tried

Select colmn1 from table1 t1, table2 t2
where t1.pid = t2.pid or t1.pid is null
and t1.colm2 is null;

But this query is returning more rows.

I want exact 110 rows. Can anybody tell me what I am doing wrong here?

ANSWER

By using all tricks in following answer. Here is the final query this may help others-

Select colmn1
from table1 t1 left join
     table2 t2
     on t1.pid = t2.pid
where (t1.colm2 is null) or (t2.pid is not null)
and t1.colm2 is null

Answer 1

First, use proper, explicit JOIN syntax. Simple rule: never use commas in the FROM clause.

Your problem could be fixed with parentheses. But it is better to use proper syntax:

Select colmn1
from table1 t1 join
     table2 t2
     on t1.pid = t2.pid
where t1.pid is null and t1.colm2 is null;

I see. The question is clearer now. You seem to want a left join :

Select colmn1
from table1 t1 left join
     table2 t2
     on t1.pid = t2.pid
where (t1.colm2 is null) or (t2.pid is not null);

This returns all rows in table1 that match the where conditions, even if they do not match the condition in table2 .

Answer 2

Operator precedence makes your query like this

...or( t1.pid is null and t1.colm2 is null;)

Use parentheses or proper JOIN syntax.

Answer 3

Adding to the answer of Gordon, you need OR condition

Select colmn1
from table1 t1 inner join
     table2 t2
     on t1.pid = t2.pid
where t1.pid is null
or t1.colm2 is null;

Answer 4

Try this,

Select colmn1 from table1 t1, table2 t2 where t1.pid = t2.pid(+) and t1.colm2 is null;

You can not compare null values on the join, please investigate about left, right, outer join, previous query indicates that you want all the records that are in both tables plus those one on table2 that has no correspondency with table1. Also check the next.

Select colmn1 from table1 t1, table2 t2 where t1.pid(+) = t2.pid and t1.colm2 is null;