I have a table like this:
Each keyword should have 4 pieces of data.
And I want to select the keywords that are less than 4 pieces of data.
I used select count(*) from mytable group by keyword to achieve something like this:
how can I select the keywords based on the count(*) result?
Here I want the keyword b from the result grid.
I am new to sql, thanks in advance.
to filter result by aggregation functions (like count) you need to use having, for example:
select keyword, count(*)
from mytable
group by keyword
having count(*) < 4
Just include having clause something like that :
select keyword
from mytable t
group by keyword
having count(*) < 4;
Related
I don't understand why I can't use this in my code :
SELECT MAX(SMTHNG), COUNT(MAX(SMTHNG))
FROM SomeTable;
Searched for an answer but didn't find it in documentation about these aggregate functions.
Also I get an SQL-compiler error "Invalid column name "SMTHNG"".
You want to know what the maximum SMTHNG in the table is with:
SELECT MAX(SMTHNG) FROM SomeTable;
This is an aggregation without GROUP BY and hence results in one single row containing the maximum SMTHNG.
Now you also want to know how often this SMTHNG occurs and you add COUNT(MAX(SMTHNG)). This, however, does not work, because you can not aggregate an aggregate directly.
This doesn't work either:
SELECT ANY_VALUE(max_smthng), COUNT(*)
FROM (SELECT MAX(smthng) AS max_smthng FROM sometable) t;
because the sub query only contains one row, so it's too late to count.
So, either use a sub query and select from the table again:
SELECT ANY_VALUE(smthng), COUNT(*)
FROM sometable
WHERE smthng = (SELECT MAX(smthng) FROM sometable);
Or count per SMTHNG before looking for the maximum. Here is how to get the counts:
SELECT smthng, COUNT(*)
FROM sometable
GROUP BY smthng;
And the easiest way to get the maximum from this result is:
SELECT TOP(1) smthng, COUNT(*)
FROM sometable
GROUP BY smthng
ORDER BY COUNT(*) DESC;
First of all, please read my comment.
Depending on what you're trying to achieve, the statement have to be changed.
If you want to count the highest values in SMTHNG field, you may try this:
SELECT T1.SMTHNG, COUNT(T1.SMTHNG)
FROM SomeTable T1 INNER JOIN
(
SELECT MAX(SMTHNG) AS A
FROM SomeTable
) T2 ON T1.SMTHNG = T2.A
GROUP BY T1.SMTHNG;
use cte like below or subquery
with cte as
(
select count(*) as cnt ,col from table_name
group by col
) select max(cnt) from cte
you can not use double aggregate function at a time on same column
I have a table that contains 10 million rows, like this:
I want to group by [CoinNameId] (this column is a foreign key) and get max value of [CreatedAt] for each [CoinNameId] group, but my query returns an error:
How can I solve this?
When you use aggregates in the select clause, every field that is not aggregated needs to be in the group by. That's why you are getting an error. I'm not sure why you had select * in your query.
You'd have to have a query like this:
SELECT CoinNameID, max([CreatedAt])
FROM [dbo].[CoinData]
GROUP BY [CoinNameID]
If you just want column CreatedAt and MAX(CreatedAt) in that case you can do like following.
SELECT CoinNameID, MAX([CreatedAt])
FROM [dbo].[CoinData]
GROUP BY [CoinNameID]
In case if you want all columns along with the MAX([CreatedAt]), you can get it like following.
SELECT *,
(SELECT MAX([CreatedAt])
FROM [dbo].[CoinData] CDI WHERE CDI.CoinNameID=CD.CoinNameID) AS MAX_CreatedAt
FROM [dbo].[CoinData] CD
You have select * on your query
SELECT
CoinNameId,MAX(CreatedAt) AS MaxCreatedAt
FROM [dbo].[CoinData]
GROUP BY CoinNameId
This will return MAX(CreatedAt) with other columns
SELECT
*, MAX([CreatedAt]) OVER (PARTITION BY [CoinNameId])
FROM [dbo].[CoinData]
There is table of numbers containing values [1,1,2,3,7,3,4,2,7]
I want to select only duplicates so output set would contain [1,2,3,7] so 4 is filtered out.
I have code that I did like this:
DROP TABLE #tempTable;
SELECT [numbers] as nums, COUNT(*) as cny
INTO #tempTable
FROM [testBase].[dbo].[numbers] group by numbers;
SELECT nums from #tempTable where nums > 1;
Now I would like to know if I can get it without first selecting to #tempTable?
Something more like select from select or is it only way I can do it?
The same in one query.
Conditions that are made after GROUP BY should be added to HAVING clause.
SELECT [numbers] as nums, COUNT(*) as cny
FROM [testBase].[dbo].[numbers]
GROUP BY numbers
HAVING COUNT(*) > 1
More on this
HAVING (Transact-SQL)
Having clause tutorial
Try this:-
SELECT [numbers] AS NUM
FROM TAB_NAME
HAVING COUNT([numbers]) > 1;
Try this..
select count(numbers) from TABLE group by numbers having count(*)>1
SELECT numbers FROM
numbers
GROUP BY numbers
having Count(numbers) >= 2
Use Having clause. Having specifies a search condition for a group or an aggregate function used in SELECT statement.. So in the having clause you can Filter the distinct rows.
SELECT [numbers]
FROM [testBase].[dbo].[numbers]
GROUP BY [numbers]
HAVING Count([numbers]) > 1
I would like to count the number of rows from a mysql table and not to include duplicate entries,
Could I use distinct with count()?
Sure.
SELECT COUNT(DISTINCT column) FROM table;
What you need is the following:
SELECT field_type_name, count(*) FROM fields GROUP BY field_type_name;
This will give you something like this:
image 14
string 75
text 9
SELECT COUNT(DISTINCT field) from Table
See this.
SELECT count(DISTINCT column Name) as alias from table_Name;
If i perform a standard query in SQLite:
SELECT * FROM my_table
I get all records in my table as expected. If i perform following query:
SELECT *, 1 FROM my_table
I get all records as expected with rightmost column holding '1' in all records. But if i perform the query:
SELECT *, COUNT(*) FROM my_table
I get only ONE row (with rightmost column is a correct count).
Why is such results? I'm not very good in SQL, maybe such behavior is expected? It seems very strange and unlogical to me :(.
SELECT *, COUNT(*) FROM my_table is not what you want, and it's not really valid SQL, you have to group by all the columns that's not an aggregate.
You'd want something like
SELECT somecolumn,someothercolumn, COUNT(*)
FROM my_table
GROUP BY somecolumn,someothercolumn
If you want to count the number of records in your table, simply run:
SELECT COUNT(*) FROM your_table;
count(*) is an aggregate function. Aggregate functions need to be grouped for a meaningful results. You can read: count columns group by
If what you want is the total number of records in the table appended to each row you can do something like
SELECT *
FROM my_table
CROSS JOIN (SELECT COUNT(*) AS COUNT_OF_RECS_IN_MY_TABLE
FROM MY_TABLE)