First sorry if i have a bad english:
select * from table2 where column1='000022071001';
Returns nothing!
select * from table1 where column1 not in (select column1 from table2);
Returns nothing
select * from table1 where column1='000022071001';
IT RETURN VALUES!
This aint logical, if column1 value '000022071001' from table1 is not in table2 , why the second query returns nothing?
What am i doing wrong?
There will be some NULL values in the column1 in the table2 causing this issue
Try this
select * from table1 where column1 not in
(select column1
from table2
WHERE column1 is not null)
Related
I am new to oracle and below is my SQL.
SELECT * FROM TABLE1 WHERE COLUMN1 = 'YES'
AND COLUMN2 IN (
CASE WHEN EXISTS(SELECT * FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%NO%')
THEN
SELECT COLUMN2 FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%YES%'
ELSE
SELECT COLUMN2 FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%YES%' END)
it is giving ORA-00936: missing expression at then statement. What am I doing wrong?
The subqueries after THEN and ELSE must be enclosed inside parentheses:
SELECT * FROM TABLE1 WHERE COLUMN1 = 'YES'
AND COLUMN2 IN (
CASE
WHEN EXISTS (SELECT * FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%NO%')
THEN (SELECT COLUMN2 FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%YES%')
ELSE (SELECT COLUMN2 FROM TABLE1 WHERE COLUMN1 = 'YES' AND COLUMN2 NOT LIKE '%YES%')
END
)
This will work only if these subqueries don't return more than 1 row.
Also, both subqueries are the same. Is this a typo?
And IN can be changed to = since CASE returns only 1 value.
I have a number of tables that mix 'real' values with nulls in columns. From exerience, issuing a SELECT against these that looks like:
SELECT column1, column2, column3 FROM mytable WHERE column1 != 'a value';
...doesn't return the records I expect. In the current table I am working on, this returns an empty recordset, even though I know I have records in the table with NULLs in column1, and other records in the table that have the value I am "!="ing in column1. I am expecting, in this case, to see the records with NULLs in column1 (and, of course, anything else if there were other not 'a value' values in column1.
Experimenting with NVL in the WHERE clause doesn't seem to give me anything different:
SELECT column1, column2, column3 FROM mytable WHERE NVL(column1, '') != 'a value';
...is also returning an empty recordset.
Using 'IS NULL' will technically give me the correct recordset in my current example, but of course if any records change to something like 'another value' in column1, then IS NULL will exclude those.
NULL can't be compared in the same way that other values can be. You must use IS NULL. If you want to include NULL values, add an OR to the WHERE clause:
SELECT column1, column2, column3 FROM mytable WHERE column1 != 'a value' OR column1 IS NULL
The query doesn't work because SQL handles equality checks (!=) different from checking if null (IS NULL).
What you could do here is something like:
SELECT column1, column2, column3
FROM mytable
WHERE column1 != 'a value' OR column1 is null;
See Not equal <> != operator on NULL.
What you were trying was correct. You just need change it a little. see below-
SELECT column1, column2, column3 FROM mytable WHERE NVL(column1, '0') != 'a value';
Instead of empty string, pass any character in NVL's second argument.
"Experimenting with NVL in the WHERE clause doesn't seem to give me anything different"
That's true:
SQL> select * from mytable;
COLUMN1 COLUMN2 COLUMN3
-------------------- ---------- ---------
a value 1 25-JUL-17
not a value 2 25-JUL-17
whatever 3 25-JUL-17
4 26-JUL-17
SQL> SELECT column1, column2, column3 FROM mytable WHERE NVL(column1, '') != 'a value';
COLUMN1 COLUMN2 COLUMN3
-------------------- ---------- ---------
not a value 2 25-JUL-17
whatever 3 25-JUL-17
SQL>
This is because your experiment didn't go far enough. For historical reasons Oracle treats an empty string as null so your nvl() statement effectively just subs one null for another. But if you had used a proper value in your call you would have got the result you wanted:
SQL> SELECT column1, column2, column3 FROM mytable WHERE NVL(column1, 'meh') != 'a value';
COLUMN1 COLUMN2 COLUMN3
-------------------- ---------- ---------
not a value 2 25-JUL-17
whatever 3 25-JUL-17
4 26-JUL-17
SQL>
The alternative approach is to explicitly test for NULL and test for the excluding value...
SQL> SELECT column1, column2, column3 FROM mytable
2 where column1 is null or column1 != 'a value';
COLUMN1 COLUMN2 COLUMN3
-------------------- ---------- ---------
not a value 2 25-JUL-17
whatever 3 25-JUL-17
4 26-JUL-17
SQL>
The second approach is probably more orthodox.
1) Undocumented Oracle function SYS_OP_MAP_NONNULL. (It exists from oracle10)
with abc as ( select 'a value' as col1 from dual
union all
select '' as col1 from dual)
select * from abc
where SYS_OP_MAP_NONNULL(col1) != SYS_OP_MAP_NONNULL('a value')
;
2) LNNVL - Check table in the documentation for clarification.
with abc as ( select 'a value' as col1 from dual
union all
select '' as col1 from dual)
select * from abc
where lnnvl( col1 = 'a value');
;
I have a table with three columns.
I query that table with IN clause.
select column1 from table1 where column1 in (1,2,3) order by column2, column3
The table1 contains only values 1 and 2 in column1. I want to return the not available value also in my result, and that should be sorted in the bottom.
example data
column1 column 2 column 3
1 100 11
2 101 50
output, the not available values should be in the last.
column1 column 2 column 3
1 100 11
2 101 50
3 null null
I tried with subquery with NVL, like select nvl((select.. in(1,2,3)),null) from dual, due to IN Clause, I am getting single row subquery returns more than one row issue, which is expected.
Also tried with the union but nothing works. Great if any help. Thanks
I think you can do it with a union all:
select column1 from table1 where column1 in (1,2,3) order by column2, column3
union all
select null from table1 where column1 not in (1,2,3) order by column2, column3
If you can't take 1,2,3 values from another table you can try with:
with t1 as (
select col1,col2,col3
from tab1
where cod_flusso in ('1','2','3')),
t2 as (
select '1' as col1,null,null
from dual
union
select '2',null,null
from dual
union
select '3',null,null
from dual)
select t2.col1,col2,col3
from t2
left outer join t1
on t1.col1= t2.col1
It's better if you can store 1,2,3 values in a second table, then use left outer join.
I want to update column1 in table1 only if the column2 in table1 match the column3 in table2.
I am trying to do using this query but I got an error that says that I am missing equal sign.
Can anyone can help?
update schema1.table1
set schema1.table1.column1
where schema1.table1.column2 = table2.column1
Your error says it all. You are not assigning any value to the column. Try to set the value using the equal = sign
You may try this:
update schema1.table1
set schema1.table1.column1 = //The value which you want to store
where schema1.table1.column2 = table2.column1
Try this query:
update schema1.table1 t1
set t1.column1 = (select t2.columnX from table2 t2
where t1.column2 = t2.column1)
where t1.column2 in (select column1 from table2)
As in the error message, you have missed an = and not assigning any value for schema1.table1.column1 in the query.
Try like this:
UPDATE schema1.table1
SET schema1.table1.column1 = <your_value>
WHERE schema1.table1.column2 = table2.column1;
I'm trying to make my query run as quickly as possible but i'm struggling to get it under 5 seconds.
I think it's because i'm referencing two linked databases
Here's my query
select column2, column3, column4
from table1#dev
where column1 in (
select distinct column2
from table2#dev
where column3 > 0
)
order by column1
Is there a way to optimise this query any more?
I've tried using join but it seems to make the query run longer
Thanks in advance
EDIT
From further investigation the DRIVING_SITE makes it run very quick like this
select /*+ DRIVING_SITE(table1) */ t1.column2, t1.column3, t1.column4
from table1#dev t1, table2#dev t2
WHERE t2.column3 > 0
But as soon as I add the distinct column2 in it makes it run really slow
First, no need for distinct. The query can be written as:
select *
from table1#dev
where column1 in (
select column2
from table2#dev
where column3 > 0
)
order by column1
Second, there are (at least) two more ways to write it. Either with JOIN:
select t1.*
from table1#dev t1
join table2#dev t2
where t2.column2 = t1.column1
and t2.column3 > 0
group by
t1.id, t1.column1, ...
order by t1.column1
or (my preference) with EXISTS:
select t1.*
from table1#dev t1
where exists
( select *
from table2#dev
where t2.column2 = t1.column1
and t2.column3 > 0
)
order by column1
In any case, you should check the execution plans for all of them.
I would expect performance to be best if you have an index on table1.column1 and for table2, either an index on column2 or a composite index on (column3, column2)
I agree with Shannon above , but are you able to create a view on the dev server ?
Also select * is a bit naughty - it is better to name the fields you really want. For very large datasets that will give you a performance improvement too.
Am I missing something in believing that this will work?
select t1.*
from table1 t1, table2 t2
where t1.column1 = t2.column2(+)
and t2.column3 > 0;