select distinct count
You can use this: SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;. This is much faster than: COUNT(DISTINCT column_name). , When you do select distinct count(id) then you are basically doing: select distinct cnt from (select count(id) as cnt from t) t;. Because the inner query only returns one row, the distinct is not doing anything. The query counts the number of rows in the
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 select distinct count 相關參考資料
SQL Server query - Selecting COUNT(*) with DISTINCT - Stack Overflow
Count all the DISTINCT program names by program type and push number. SELECT COUNT(DISTINCT program_name) AS Count, program_type AS [Type] FROM cm_production WHERE push_number=@push_number GROUP BY pr... https://stackoverflow.com performance - postgresql COUNT(DISTINCT ...) very slow - Stack ...
You can use this: SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;. This is much faster than: COUNT(DISTINCT column_name). https://stackoverflow.com select distinct count(id) vs select count(distinct id) - Stack ...
When you do select distinct count(id) then you are basically doing: select distinct cnt from (select count(id) as cnt from t) t;. Because the inner query only returns one row, the distinct is not doi... https://stackoverflow.com sql - What's the difference between select distinct count, and ...
Query select count(distinct a) will give you number of unique values in a. While query select distinct count(a) will give you list of unique counts of values in a. Without grouping it will be just on... https://stackoverflow.com sql - What exactly does SELECT DISTINCT(COUNT(*)) do? - Stack Overflow
Distinct is not required in your SQL ,as you are going to get only result, count(*) without group by clause returns, count of all rows within that table. Hence try this : select count(*) from table1.... https://stackoverflow.com MySQL Select Distinct Count - Stack Overflow
If you want to get the total count for each user, then you will use: select user_id, count(distinct video_id) from data group by user_id;. Then if you want to get the total video_ids then you will wr... https://stackoverflow.com SQL COUNT - 1Keydata SQL 語法教學
"IS NOT NULL" 是"這個欄位不是空白" 的意思。 COUNT 和DISTINCT 經常被合起來使用，目的是找出表格中有多少筆不同的資料(至於這些資料實際上是什麼並不重要)。舉例來說，如果我們要找出我們的表格中有多少個不同的Store_Name，我們就鍵入，. SELECT COUNT (DISTINCT Store_Name) FROM Stor... https://www.1keydata.com SQL SELECT DISTINCT | COUNT | ROWS | On one columns | Examples
SQL SELECT DISTINCT with COUNT on ROWS or on one columns. http://www.dofactory.com SQL COUNT DISTINCT 函数 - w3school 在线教程
定义和用法. 可以一同使用DISTINCT 和COUNT 关键词，来计算非重复结果的数目。 语法. SELECT COUNT(DISTINCT column(s)) FROM table. 例子. 注意：下面的例子仅适用于ORACLE 和Microsoft SQL server，不能用于Microsoft Access。 "Orders"表：. Company, OrderNu... http://www.w3school.com.cn SQL SELECT DISTINCT Statement - W3Schools
SELECT COUNT(DISTINCT Country) FROM Customers;. Try it Yourself ». Note: The example above will not work in Firefox and Microsoft Edge! Because COUNT(DISTINCT column_name) is not supported in Microsof... https://www.w3schools.com |