2009年8月3日 · SELECT COUNT(1) FROM dbo.tab800krows SELECT COUNT(1),FKID FROM dbo.tab800krows GROUP BY FKID SELECT COUNT(*) FROM dbo.tab800krows SELECT COUNT(*),FKID FROM dbo.tab800krows GROUP BY FKID Same IO, same plan, the works. Edit, Aug 2011. Similar question on DBA.SE. Edit, Dec 2011. COUNT(*) is mentioned specifically in …

2010年4月26日 · count(1): The one-trick pony. In particular to COUNT(1), it is a one-trick pony, it works well only on one table query: SELECT COUNT(1) FROM tbl But when you use joins, that trick won't work on multi-table queries without its semantics being confused, and in …

2018年9月5日 · The expression count++ evaluates count, adds 1, stores the result in count, but the overall result (the net value of count++) is the original value of count. The expression count + 1 evaluates count, adds 1, and returns the result. The value of count is not changed. Interestingly, while it's possible to mimic ++count (pre-increment) with an ...

I've seen DBAs, when counting the number of rows, run SELECT COUNT(1) FROM table;. What is the 1 in the query? I've tried putting in other numbers (2, 0, -1) and result is always the same as using 1.

2011年8月19日 · According to another similar question (Count(*) vs Count(1)), they are the same. In Oracle, according to Ask Tom, count(*) is the correct way to count the number of rows because the optimizer changes count(1) to count(*). count(1) actually means to count rows with non-null 1's (all of them are non-null so optimizer will change it for you).

2013年8月17日 · COUNT(*) will count the number of rows, while COUNT(expression) will count non-null values in expression and COUNT(column) will count all non-null values in column. Since both 0 and 1 are non-null values, COUNT(0)=COUNT(1) and they both will be equivalent to the number of rows COUNT(*). It's a different concept, but the result will be the same.

2008年10月8日 · Also count(1) here 1 is not coloumn no, it is a expression. e.g) select 1 from table1; will print 1 no of times for no of rows that table has. – Kanagavelu Sugumar Commented Feb 13, 2013 at 12:13

2018年1月11日 · COUNT(*) cuenta los registros de la SELECT guardando en memoria las columnas de las consultas, es decir si en la consulta tienes 20 columnas y 300 registros, el guardara los 6000 espacios en memoria con su data. lo …

2018年7月22日 · count(1) and count(*) are now same in oracle both uses index if available and count Nulls too. count(1) simply replaces rows data with 1 and then count number of 1's and count(*) counts rows may be on the basis of rowids.

SELECT user_id, COUNT(*) count FROM PAYMENT GROUP BY account, user_id, date HAVING COUNT(*) > 1 Update If you want to only include those that have a distinct ZIP you can get a distinct set first and then perform you HAVING/GROUP BY