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;
Related
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;
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]
Is a SQL function exists to SUM some numbers in a column but only if they are different ?
You can use subqueries to achive this:
Select Sum(TBL.column) From
( Select distinct column From Table) as TBL
SELECT SUM(DISTINCT(COLUMN_NAME)) FROM TABLE
Looking for sql to get distinct names and count of those names from a sql table:
Structure:
id
name
other details
Do I use distinct to get each group and then count through those to get:
name1 count(name1)
name2 count(name2)
etc
Thanks
Rob.
When you want a COUNT() or a SUM(), you're using an AGGREGATE FUNCTION based on a GROUP BY clause.
As GROUP BY brings together all records with the same values specified in the GROUP BY columns, you're already getting the same effect as DISTINCT.
Except that DISTINCT doesn't allow aggregates, and GROUP BY does.
SELECT
name,
COUNT(*) AS count_of_name
FROM
yourTable
GROUP BY
name
Try :
SELECT *, COUNT(*) FROM my_table GROUP BY name
Something like this?
select name,COUNT(name) FROM Persons GROUP BY name
In the end I used:
SELECT DISTINCT `school`,COUNT(`school`) AS cat_num FROM table GROUP BY school order by cat_num DESC
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)