This is my records.
I just want to delete records with
PACK = '1`S'
but if the row does not have any duplicates even if its PACK is equals to '1`S' it will remain.
The only thing I can do is to check the records that have duplicates.
And to delete records with PACK = 1's.
SELECT Name, COUNT(*) as duplicates
FROM table1
Group by Name
having COUNT(*) >1
Order by duplicates
Note: I just replace delete with select.
SELECT * FROM table1 WHERE PACK = '1's'
So you want to delete any 1`S records for which exists a record with the same name and category and another pack. You can word exactly this in SQL:
delete from table1
where pack = '1`S'
and exists
(
select *
from table1 other
where other.name = table1.name
and other.category = table1.category
and other.pack <> table1.pack
);
This is standard SQL and should work in about every DBMS. With MySQL being the notorious exception, as they forbid to directly use the updated table in a subquery again. Here you'd have to replace from table1 other by from (select * from table1) other.
Maybe this pl/sql can guide you:
Delete from table1
where id not in (select min(id)
from table1
where pack = '1`S'
group by name
having count(*) = 1
)
and pack = '1`S';
INNER JOIN the table on itself with the restriction that the ID field is larger than the ID field found by the join. If there are no duplicates there will not be any results. If there are duplicates the most recently added will be deleted.
Related
I'have a little question about a query.
I have to update a column from a table where there are only record of expense(integer).
I must increase the expense of 5% if the client is from a specific state, the column of the state is in a different table and the key in common is the address.
This is my query below :
UPDATE table 1 a
SET expense_vl = (
SELECT expense*1.05 FROM table 1
LEFT JOIN table2 b ON b.ADDRESS_ID=a.ADDRESS_ID
WHERE description_state IN 'lollyland'
)
I'd recommend using a semi-join:
update table_1 a
set expense_v1 = expense * 1.05
where exists (
select null
from table2 b
where
a.address_id = b.address_id and
b.description_state = 'lollyland'
)
Althought I must add that it would help if you include the DDL for your table. We're sort of guessing at which table "description" came from.
Also, when possible, include sample input for each table and desired output. We don't need a million records, just an example that illustrates your issue.
Try below
UPDATE table1 a SET expense_vl = (SELECT expense*1.05
FROM table2 b
WHERE b.ADDRESS_ID=a.ADDRESS_ID)
WHERE description_state IN 'lollyland'
Or try with subselect:
UPDATE table1
SET expense_vl = expense*1.05
WHERE ADDRESS_ID IN (SELECT ADDRESS_ID FROM table2 WHERE description_state IN 'lollyland')
I think you need to change your query like below :
UPDATE table 1 A
SET expense_vl=expense*1.05 FROM table 1
LEFT JOIN table2 B ON B.ADDRESS_ID=A.ADDRESS_ID
WHERE B.description_state IN 'lollyland'
table1 (id, name)
table2 (id, name)
Query:
SELECT name
FROM table2
-- that are not in table1 already
SELECT t1.name
FROM table1 t1
LEFT JOIN table2 t2 ON t2.name = t1.name
WHERE t2.name IS NULL
Q: What is happening here?
A: Conceptually, we select all rows from table1 and for each row we attempt to find a row in table2 with the same value for the name column. If there is no such row, we just leave the table2 portion of our result empty for that row. Then we constrain our selection by picking only those rows in the result where the matching row does not exist. Finally, We ignore all fields from our result except for the name column (the one we are sure that exists, from table1).
While it may not be the most performant method possible in all cases, it should work in basically every database engine ever that attempts to implement ANSI 92 SQL
You can either do
SELECT name
FROM table2
WHERE name NOT IN
(SELECT name
FROM table1)
or
SELECT name
FROM table2
WHERE NOT EXISTS
(SELECT *
FROM table1
WHERE table1.name = table2.name)
See this question for 3 techniques to accomplish this
I don't have enough rep points to vote up froadie's answer. But I have to disagree with the comments on Kris's answer. The following answer:
SELECT name
FROM table2
WHERE name NOT IN
(SELECT name
FROM table1)
Is FAR more efficient in practice. I don't know why, but I'm running it against 800k+ records and the difference is tremendous with the advantage given to the 2nd answer posted above. Just my $0.02.
SELECT <column_list>
FROM TABLEA a
LEFTJOIN TABLEB b
ON a.Key = b.Key
WHERE b.Key IS NULL;
https://www.cloudways.com/blog/how-to-join-two-tables-mysql/
This is pure set theory which you can achieve with the minus operation.
select id, name from table1
minus
select id, name from table2
Here's what worked best for me.
SELECT *
FROM #T1
EXCEPT
SELECT a.*
FROM #T1 a
JOIN #T2 b ON a.ID = b.ID
This was more than twice as fast as any other method I tried.
Watch out for pitfalls. If the field Name in Table1 contain Nulls you are in for surprises.
Better is:
SELECT name
FROM table2
WHERE name NOT IN
(SELECT ISNULL(name ,'')
FROM table1)
You can use EXCEPT in mssql or MINUS in oracle, they are identical according to :
http://blog.sqlauthority.com/2008/08/07/sql-server-except-clause-in-sql-server-is-similar-to-minus-clause-in-oracle/
That work sharp for me
SELECT *
FROM [dbo].[table1] t1
LEFT JOIN [dbo].[table2] t2 ON t1.[t1_ID] = t2.[t2_ID]
WHERE t2.[t2_ID] IS NULL
You can use following query structure :
SELECT t1.name FROM table1 t1 JOIN table2 t2 ON t2.fk_id != t1.id;
table1 :
id
name
1
Amit
2
Sagar
table2 :
id
fk_id
email
1
1
amit#ma.com
Output:
name
Sagar
All the above queries are incredibly slow on big tables. A change of strategy is needed. Here there is the code I used for a DB of mine, you can transliterate changing the fields and table names.
This is the strategy: you create two implicit temporary tables and make a union of them.
The first temporary table comes from a selection of all the rows of the first original table the fields of which you wanna control that are NOT present in the second original table.
The second implicit temporary table contains all the rows of the two original tables that have a match on identical values of the column/field you wanna control.
The result of the union is a table that has more than one row with the same control field value in case there is a match for that value on the two original tables (one coming from the first select, the second coming from the second select) and just one row with the control column value in case of the value of the first original table not matching any value of the second original table.
You group and count. When the count is 1 there is not match and, finally, you select just the rows with the count equal to 1.
Seems not elegant, but it is orders of magnitude faster than all the above solutions.
IMPORTANT NOTE: enable the INDEX on the columns to be checked.
SELECT name, source, id
FROM
(
SELECT name, "active_ingredients" as source, active_ingredients.id as id
FROM active_ingredients
UNION ALL
SELECT active_ingredients.name as name, "UNII_database" as source, temp_active_ingredients_aliases.id as id
FROM active_ingredients
INNER JOIN temp_active_ingredients_aliases ON temp_active_ingredients_aliases.alias_name = active_ingredients.name
) tbl
GROUP BY name
HAVING count(*) = 1
ORDER BY name
See query:
SELECT * FROM Table1 WHERE
id NOT IN (SELECT
e.id
FROM
Table1 e
INNER JOIN
Table2 s ON e.id = s.id);
Conceptually would be: Fetching the matching records in subquery and then in main query fetching the records which are not in subquery.
First define alias of table like t1 and t2.
After that get record of second table.
After that match that record using where condition:
SELECT name FROM table2 as t2
WHERE NOT EXISTS (SELECT * FROM table1 as t1 WHERE t1.name = t2.name)
I'm going to repost (since I'm not cool enough yet to comment) in the correct answer....in case anyone else thought it needed better explaining.
SELECT temp_table_1.name
FROM original_table_1 temp_table_1
LEFT JOIN original_table_2 temp_table_2 ON temp_table_2.name = temp_table_1.name
WHERE temp_table_2.name IS NULL
And I've seen syntax in FROM needing commas between table names in mySQL but in sqlLite it seemed to prefer the space.
The bottom line is when you use bad variable names it leaves questions. My variables should make more sense. And someone should explain why we need a comma or no comma.
I tried all solutions above but they did not work in my case. The following query worked for me.
SELECT NAME
FROM table_1
WHERE NAME NOT IN
(SELECT a.NAME
FROM table_1 AS a
LEFT JOIN table_2 AS b
ON a.NAME = b.NAME
WHERE any further condition);
I have a table (A) with a list of order numbers. It contains a single row.
Once this order has been processed it should be deleted. However, it is failing to be deleted.
I began investigating, a really simple query is performed for the deletion.
delete from table(A) where orderno not in (select distinct orderno from tableB)
The order number absolutely does not exist in tableB.
I changed the query in SSMS to :
select * from table(A) where orderno not in (select distinct orderno from tableB)
This returned 0 rows. Bare in mind the orderno does exist in tableA.
I then changed the query from "not in" to "In". It still returned 0 rows. How can this be possible that a value is not in a list of values but also not show for the opposite?
Things I have tried:
Two additional developers to look over it.
ltrim(rtrim()) on both the select values.
Various char casts and casting the number as an int.
Has anyone experienced this?
Don't use NOT IN with a subquery. Use NOT EXISTS instead:
delete from tableA
where not exists (select 1 from tableB where tableA.orderno = tableB.orderno);
What is the difference? If any orderno in TableB is NULL, then NOT IN returns NULL. This is correct behavior based on how NULL is defined in SQL, but it is counterintuitive. NOT EXISTS does what you want.
You can use not exists
select *
from table(A) a
where not exists (selet 1 from tableB where orderno = a.orderno);
I have experienced the same.
try joining the two tables tableA and TableB
select * from TableA a
inner join TableB b on a.orderno =b.orderno
This should allow you to get the records and then you can delete the same.
I have two datasets on two seperate servers. They both pull one column of information each.
I would like to build a report showing the values of the rows that only appear in one of the datasets.
From what I have read, it seems I would like to do this on the SQL side, not the reporting side; I am not sure how to do that.
If someone could shed some light on how that is possible, I would really appreciate it.
You can use the NOT EXISTS clause to get the differences between the two tables.
SELECT
Column
FROM
DatabaseName.SchemaName.Table1
WHERE
NOT EXISTS
(
SELECT
Column
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
Table1.Column = Table2.Column --looks at equalities, and doesn't
--include them because of the
--NOT EXISTS clause
)
This will show the rows in Table1 that don't appear in Table2. You can reverse the table names to find the rows in Table2 that don't appear in Table1.
Edit: Made an edit to show what the case would be in the event of linked servers. Also, if you wanted to see all of the rows that are not shared in both tables at the same time, you can try something as in the below.
SELECT
Column, 'Table1' TableName
FROM
DatabaseName.SchemaName.Table1
WHERE
NOT EXISTS
(
SELECT
Column
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
Table1.Column = Table2.Column --looks at equalities, and doesn't
--include them because of the
--NOT EXISTS clause
)
UNION
SELECT
Column, 'Table2' TableName
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
NOT EXISTS
(
SELECT
Column
FROM
DatabaseName.SchemaName.Table1
WHERE
Table1.Column = Table2.Column
)
You can also use a left join:
select a.* from tableA a
left join tableB b
on a.PrimaryKey = b.ForeignKey
where b.ForeignKey is null
This query will return all records from tableA that do not have corresponding records in tableB.
If you want rows that appear in exactly one data set and you have a matching key on each table, then you can use a full outer join:
select *
from table1 t1 full outer join
table2 t2
on t1.key = t2.key
where t1.key is null and t2.key is not null or
t1.key is not null and t2.key is null
The where condition chooses the rows where exactly one match.
The problem with this query, though, is that you get lots of columns with nulls. One way to fix this is by going through the columns one by one in the SELECT clause.
select coalesce(t1.key, t2.key) as key, . . .
Another way to solve this problem is to use a union with a window function. This version brings together all the rows and counts the number of times that key appears:
select t.*
from (select t.*, count(*) over (partition by key) as keycnt
from ((select 'Table1' as which, t.*
from table1 t
) union all
(select 'Table2' as which, t.*
from table2 t
)
) t
) t
where keycnt = 1
This has the additional column specifying which table the value comes from. It also has an extra column, keycnt, with the value 1. If you have a composite key, you would just replace with the list of columns specifying a match between the two tables.
I need to select all IDs from one table with columns ID and X, WHERE X = 'Y'. For each of those IDs, I need to look up some stuff in a different table:
If the ID does not exist, it gets no row in the final result.
If the ID does exist, I want to do some logic to figure out if it gets a row. For simplicity, assume that the logic is: if column Q > 0.
So the final result is simply a column of IDs, throwing out some because they are disqualified for one of two reasons as above.
thanks.
This is what JOINs are made for.
SELECT table1.* FROM table1
INNER JOIN table2
ON table1.ID = table2.table1_ID
AND table2.Q > 0;
This will select all records in table1 (which have IDs) and then remove any records that do not have a matching record in table2 or do not have a Q > 0.
If I got your question right this might be what you are looking for:
select id from your_table
where X = 'Y'
and id in (select id from other_table where Q > 0)
You can use a subquery:
SELECT id FROM table1 WHERE table1.id IN (SELECT q FROM table2 WHERE table2.q > 0) AND table1.x='y'
SQL will check to see if the results from the outermost query are in the subquery (the part in parentheses) and won't return anything if they aren't.