I have a table with two column, values of one column is null and another column have many duplicated values and blanks. how can I remove duplicated values and blanks from that column by a query?
You can use temporary table for this task as below:
SELECT DISTINCT * INTO #tmpTable FROM MyTable
TRUNCATE TABLE MyTable
INSERT INTO MyTable SELECT * FROM #tmpTable
You can create an empty copy of the table. Then you run an INSERT INTO new_table SELECT DISTINCT * FROM old_table. Finally, drop the old table and rename the new one.
One way of doing this - using CTE
create table #dups (col1 int, col2 int)
insert into #dups
select null,null union all
select null,1 union all
select null,1 union all
select null,1 union all
select null,2 union all
select null,2 union all
select null,3 union all
select null,null
select * from #dups
;WITH cte
AS (SELECT col1,col2,ROW_NUMBER() OVER (PARTITION BY Col1,Col2
ORDER BY ( SELECT 0)) RN
FROM #dups
)
DELETE FROM cte
WHERE RN > 1 OR col2 is null
1) If you want to keep the row with the lowest id value:
DELETE n1 FROM names n1, names n2 WHERE n1.id > n2.id AND n1.name = n2.name
2) If you want to keep the row with the highest id value:
DELETE n1 FROM names n1, names n2 WHERE n1.id < n2.id AND n1.name = n2.name
Please get the copy of your table before processing this.
if don't get than send me table name i will put replace your table name.
It is tested with MySQL 5.1
Not sure about other versions
see the link
Delete all Duplicate Rows except for One in MySQL?
If I understood right, you want to avoid for the column2 NULL and blanks?
SELECT COLUMN1, COLUMN2 FROM TABLE
GROUP BY
COLUMN1, COLUMN2
WHERE
COLUMN2 NOT NULL AND COULMN2 <> ''
This query is going to show results only when the COLUMN2 has some data.
try this
DELETE FROM [Table]
WHERE (ColmnB IN
(SELECT ColumnB
FROM [Table] AS Table_1
GROUP BY ColumnB
HAVING (COUNT(*) > 1))) OR
(RTRIM(LTRIM(ISNULL(ColumnB,''))) = '')
table has tow column . first column is null value . second column has duplicate value and blank value.
Related
I've got a query like this
select column, count(*)
from mytable
where column in ('XXX','YYY','ZZZ',....)
group by column;
But I want also to get a row for values the aren't in the table.
Let's suppose that 'ZZZ' doesn't exist in mytable, I'd like to get:
COLUMN COUNT(*)
XXX 3
YYY 2
ZZZ 0 (or NULL)
Oracle version 10g
Thanks in advance
Mark
In general, you would need to have a second table which contains all the possible column values whose counts you want to appear in the output. For demo purposes only, we can use a CTE for that:
WITH vals AS (
SELECT 'XXX' AS val UNION ALL
SELECT 'YYY' UNION ALL
SELECT 'ZZZ'
)
SELECT t1.val, COUNT(t2.col) AS cnt
FROM vals t1
LEFT JOIN mytable t2
ON t2.col = t1.val
GROUP BY
t1.val;
I know that in SQL Server, one can use SELECT clause without FROM clause, and create a table with one row and one column
SELECT 1 AS n;
But I was just wondering, is it possible to use SELECT clause without FROM clause, to create
a table with one column and multiple rows
a table with multiple columns and one row
a table with multiple columns and multiple rows
I have tried many combinations such as
SELECT VALUES(1, 2) AS tableName(n, m);
to no success.
You can do it with CTE and using union(Use union all if you want to display duplicates)
Rextester Sample for all 3 scenarios
One Column and multiple rows
with tbl1(id) as
(select 1 union all
select 2)
select * from tbl1;
One row and multiple columns
with tbl2(id,name) as
(select 1,'A')
select * from tbl2;
Multiple columns and multiple rows
with tbl3(id,name) as
(select 1,'A' union all
select 2,'B')
select * from tbl3;
-- One column, multiple rows.
select 1 as ColumnName union all select 2; -- Without FROM;
select * from ( values ( 1 ), ( 2 ) ) as Placeholder( ColumnName ); -- With FROM.
-- Multiple columns, one row.
select 1 as TheQuestion, 42 as TheAnswer; -- Without FROM.
select * from ( values ( 1, 42 ) ) as Placeholder( TheQuestion, TheAnswer ); -- With FROM.
-- Multiple columns and multiple rows.
select 1 as TheQuestion, 42 as TheAnswer union all select 1492, 12; -- Without FROM.
select * from ( values ( 1, 2 ), ( 2, 4 ) ) as Placeholder( Column1, Column2 ); -- With FROM.
You can do all that by using UNION keyword
create table tablename as select 1 as n,3 as m union select 2 as n,3 as m
In Oracle it will be dual:
create table tablename as select 1 as n,3 as m from dual union select 2 as n,3 as m from dual
You can use UNION operator:
CREATE TABLE AS SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;
The UNION operator selects only distinct values by default. To allow duplicate values you can use UNION ALL.
The column names in the result-set are usually equal to the column names in the first SELECT statement in the UNION.
try this:
--1) a table with one column and multiple rows
select * into tmptable0 from(
select 'row1col1' as v1
union all
select 'row2col1' as v1
) tmp
--2) a table with multiple columns and one row
select 'row1col1' as v1, 'row1col2' as v2 into tmptable1
--3) a table with multiple columns and multiple rows
select * into tmptable2 from(
select 'row1col1' as v1, 'row1col2' as v2
union all
select 'row2col1' as v2, 'row2col2' as v2
) tmp
One can create a view and later can query it whenever required
-- table with one column and multiple rows
create view vw1 as
(
select 'anyvalue' as col1
union all
select 'anyvalue' as col1
)
select * from vw1
-- table with multiple columns and multiple rows
create view vw2 as
(
select 'anyvalue1' as col1, 'anyvalue1' as col2
union all
select 'anyvalue2' as col1, 'anyvalue2' as col2
)
select * from vw2
I want to delete all records that are returned by a certain query, but I can't figure out a proper way to do this. I tried to DELETE FROM mytable WHERE EXISTS (subquery), however, that deleted all records from the table and not just the ones selected by the subquery.
My subquery looks like this:
SELECT
MAX(columnA) as columnA,
-- 50 other columns
FROM myTable
GROUP BY
-- the 50 other columns above
having count(*) > 1;
This should be easy enough, but my mind is just stuck right now. I'm thankful for any suggestions.
Edit: columnA is not unique (also no other column in that table is globally unique)
Presumably, you want to use in:
DELETE FROM myTable
WHERE columnA IN (SELECT MAX(columnA) as columnA
FROM myTable
GROUP BY -- the 50 other columns above
HAVING count(*) > 1
);
This assumes that columnA is globally unique in the table. Otherwise, you will have to work a bit harder.
DELETE FROM myTable t
WHERE EXISTS (SELECT 1
FROM (SELECT MAX(columnA) as columnA,
col1, col2, . . .
FROM myTable
GROUP BY -- the 50 other columns above
HAVING count(*) > 1
) t2
WHERE t.columnA = t2.columnA AND
t.col1 = t2.col1 AND
t.col2 = t2.col2 AND . . .
);
And, even this isn't guaranteed to work if any of the columns have NULL values (although the conditions can be easily modified to handle this).
Another solution if the uniqueness is only guaranteed by a set of columns:
delete table1 where (col1, col2, ...) in (
select min(col1), col2, ...
from table1
where...
group by col2, ...
)
Null values will be ignored and not deleted.
To achieve this, try something like
with data (id, val1, val2) as
(
select 1, '10', 10 from dual union all
select 2, '20', 21 from dual union all
select 2, null, 21 from dual union all
select 2, '20', null from dual
)
-- map null values in column to a nonexistent value in this column
select * from data d where (d.id, nvl(d.val1, '#<null>')) in
(select dd.id, nvl(dd.val1, '#<null>') from data dd)
If you need to delete all the rows of a table such that the value of a given field is in the result of a query, you can use something like
delete table
my column in ( select column from ...)
COUNT(DATECREATED)
88708
26625
17092
how to create a select query for viewing this three values in single column as different column names like
COUNT(DATECREATED) COUNT(DATECREATED) COUNT(DATECREATED)
88708 26625 17092
88708
88708
If you just want 1 row with 3 rows as columns, then use this. Here col is the alias for your count statement.
with tbl as
(select rownum as rno,col from
(your existing query) t
)
select (select col from tbl where rno=1) col1 ,
(select col from tbl where rno=2) col2,
(select col from tbl where rno=3 ) col3
from dual
If there are more rows and you want to use them as column, then read about Dynamic pivot in Oracle and you shall get your answer.
Finally i did like this.. Thanks all for quick reply
select sum(colname) as aliasname, sum(colname) as aliasname, sum(colname) as aliasname from
(select count(colname) as colname,0 as colname,0 as colname from cof
union all
select 0,count(colname),0 from cof where colname is not null
union all
select 0,0,count(colname) from cof where colname is not null);
i would like to run a sql statement that will delete ONLY the second value for example
delete from table1 where condition1
i want this statement to delete ONLY the second value
how can i accomplish this?
i would like to clarify. i have a field called field1 which is an autonumber and and it is a primary key and it increments. i would like to delete the record containing the greater number
You could also employ the ROW_NUMBER() function of SQL server to number each row, and use this number to isolate just the second item for deletion, according to your own custom ordering in the inner query ( over (ORDER BY <myKey> asc) ). This provides a great deal of flexibility.
DELETE a FROM table1
FROM table1 a
JOIN (
select ROW_NUMBER() over (ORDER BY <myKey> asc) as AutoNumber, <myKey> from table1
) b on a.<myKey> = b.<myKey>
WHERE condition1
AND b.AutoNumber = 2
Do you want to delete only the last duplicate, or all but the first?
For all but the first: (Edited to use CTE per #Martin's suggestion.)
with target as (select * from table1 where condition1)
delete from target goner
where exists (select * from target keeper
where keeper.field1 < goner.field1)
In other words, if there is another matching record with a lower field1, delete this record.
EDIT:
To delete only the last:
with target as (select * from table1 where condition1)
delete from target goner
where exists (select * from target keeper
where keeper.field1 < goner.field1)
and not exists (select * from target missing
where missing.field1 > goner.field1)
In other words, if there is another matching record with a lower field1, AND there is no matching record with a higher field1, then we have the highest duplicate, so nuke it.
It's been a while (so my syntax my not quite be right), and this may not be the best solution, but the "academic" answer would be something like:
delete from table1 where condition1
and field1 = (select max(field1) from table1 where condition1)
Try this:
DELETE MyTable
FROM MyTable
LEFT OUTER JOIN (
SELECT MIN(id) as id, Col1, Col2, Col3
FROM MyTable
GROUP BY Col1, Col2, Col3
) as KeepRows ON
MyTable.id= KeepRows.id
WHERE
KeepRows.RowId IS NULL
UPDATE
While this might not be as "pretty" as #Jeffrey's it works. From what I can tell, #Jeffrey's does not. See sql below (Delete replaced with SELECT * for demonstration):
WITH TEMP as
(
SELECT 1 as id,'A' as a,'Z' as b
UNION
SELECT 2,'A','Z'
UNION
SELECT 3,'B','Z'
UNION
SELECT 4,'B','Z'
)
SELECT *
FROM TEMP
LEFT OUTER JOIN (
SELECT MIN(id) as id, a, b
FROM TEMP
GROUP BY a, b
) as KeepRows ON
temp.id= KeepRows.id
WHERE
KeepRows.id IS NULL