Notice that the Group By puts together rows into sets (depending on the column_list) and the aggregate function returns a summary value (count, min, max or average).
Make sure all fields in the select list also appear in the Group By list.
First example on how to use the Group By, here is the Contact Table
|1||White||Alan||210 George St||Sydney||NSW||2000|
|2||Johnson||Benjamin||11 Cooper St||Surry Hill||NSW||2010|
|3||Brown||Peter||72 Haymarket St||Haymarket||NSW||2000|
|4||Anderson||Thomas||33 Collins St||Melbourne||VIC||3000|
|5||Gomdas||Tony||78 Marine Pde||Coolangatta||QLD||4225|
|6||Jones||David||2 Park St||Sydney||NSW||2000|
|7||Gutman||Philip||27 Swanson St||Melbourne||VIC||3000|
You can add an extra layer to the grouping by selecting one more column in the SELECT statement. Another word, you are creating a subset of the first column.
The following SQL gives an error, see if you can spot the problem!
Have you spotted the issue?
The above Sql shows a common mistake when you use Sql Group By. The issue here is that we didn't put all columns that we use in the Select statement. To fix it, just match the column_list in Select statement with the column_list in the Group By. The correct Sql is the same as the second example above.
The core of Sql, selecting data from table.
Conditionally selecting rows from table.
Eliminating duplicate values in the output.
Counting number of rows.
Getting the sum of a field
This function will return the highest value.
This function will return the lowest value.
This function will return the average value.
Sql Order By
Sorting the output
Sql And Or
Connecting two or more conditions in the Where or Having clause.
To filter the result of aggregation
Pattern searching for conditions in Where or Having clause
Added to conditions to show results between two values.
Return from Sql Group By to Sql Commands
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