aggregate-functions

I have a problem with a query in Oracle SQL. I have a first_name column in an employees table. I want to group my records according to the first character in first_name . For example, I have 26 records, one with name = 'Alice' , one with name = 'Bob' , and so on down the alphabet for each name's first character. After the query, there should be 26 groups with one employee each. I tried the following, but it's not working: SELECT employee_id, (SUBSTR(first_name,1,1)) AS alpha FROM employees GROUP BY alpha; name_which_starts_from employees A 10 B 2 C 4 D 9 E 3 G 3 H 3 I 2 J 16 K 7 L 6 M 6 N 4 O

I have 2 tables - an Account table and a Users table. Each account can have multiple users. I have a scenario where I want to execute a single query/join against these two tables, but I want all the Account data (Account.*) and only the first set of user data (specifically their name). Instead of doing a "min" or "max" on my aggregated group, I wanted to do a "first". But, apparently, there is no "First" aggregate function in TSQL. Any suggestions on how to go about getting this query? Obviously, it is easy to get the cartesian product of Account x Users: SELECT User.Name, Account.* FROM

I am using count and group by to get the number of subscribers registered each day: SELECT created_at, COUNT(email) FROM subscriptions GROUP BY created at; Result: created_at count ----------------- 04-04-2011 100 05-04-2011 50 06-04-2011 50 07-04-2011 300 I want to get the cumulative total of subscribers every day instead. How do I get this? created_at count ----------------- 04-04-2011 100 05-04-2011 150 06-04-2011 200 07-04-2011 500 With larger datasets, window functions are the most efficient way to perform these kinds of queries -- the table will be scanned only once, instead of once for

I have a table like this: way stop time 1 1 00:55 1 2 01:01 1 3 01:07 2 2 01:41 2 3 01:47 2 5 01:49 3 1 04:00 3 2 04:06 3 3 04:12 and I want a table like this: stop way_1 way_2 way_3 (way_n) 1 00:55 04:00 2 01:01 01:41 04:06 3 01:07 01:47 04:12 5 01:49 There are many solutions online about MySQL cross tab (pivot table), but how can I do this if I don't know how many "way" are there? Thanks The number and names of columns must be fixed at the time you prepare the query. That's just the way SQL works. So you have two choices of how to solve this. Both choices involve writing application code: (1

I am trying to group some records into 5-, 15-, 30- and 60-minute intervals: SELECT AVG(value) as "AvgValue", sample_date/(5*60) as "TimeFive" FROM DATA WHERE id = 123 AND sample_date >= 3/21/2012 i want to run several queries, each would group my average values into the desired time increments. So the 5-min query would return results like this: AvgValue TimeFive 6.90 1995-01-01 00:05:00 7.15 1995-01-01 00:10:00 8.25 1995-01-01 00:15:00 The 30-min query would result in this: AvgValue TimeThirty 6.95 1995-01-01 00:30:00 7.40 1995-01-01 01:00:00 The datetime column is in yyyy-mm-dd hh:mm:ss