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SQL GROUP BY Command for more than one field with sub groupingPlease read basic of group by command Part I
We know by using count command and group by command we can find out the total records in a particular group of data. Now we will try to apply group by command including two different fields and we will break the groups and get total records for each sub-group also. This way we will get total of each subgroup also. This can be further improved by adding SQL HAVING command with the group by command.
For this example you can download the query file to create the table with some data inside it. Inside this table there are records of documents saying details of the records. The records belongs to one category( management or Computers) and then belong to one type ( Book, CD or report )
Here is the full table with all the rows. On this we will apply the group by query
| d_id |
name |
type |
category |
price |
stock |
| 1 |
Book1 |
Book |
Management |
220 |
10 |
| 2 |
Book2 |
CD |
Management |
120 |
8 |
| 3 |
Book3 |
Report |
Management |
25 |
4 |
| 4 |
Book4 |
Book |
Management |
55 |
8 |
| 5 |
Document1 |
Book |
Management |
15 |
23 |
| 6 |
Document2 |
CD |
Computers |
80 |
45 |
| 7 |
Document3 |
Report |
Computers |
55 |
65 |
| 8 |
Book5 |
Report |
Management |
80 |
10 |
| 9 |
Document4 |
CD |
Management |
72 |
5 |
| 10 |
Book 8 |
Book |
Computers |
88 |
6 |
| 11 |
Book 9 |
CD |
Computers |
100 |
5 |
| 12 |
Document5 |
Report |
Computers |
85 |
8 |
| 13 |
Book 10 |
Book |
Computers |
150 |
5 |
Here is the SQL group by command applied on the above table.
SELECT category,type, count(*) as total FROM `documents` group by category,type
This will display the total records in each group and sub group. Like this
| category |
type |
total |
| Computers |
Book |
2 |
| Computers |
CD |
2 |
| Computers |
Report |
2 |
| Management |
Book |
3 |
| Management |
CD |
2 |
| Management |
Report |
2 |
Download the SQL group by query file to create the table with data
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| | Floris | 13-09-2011 |
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| Hi, I hope somebody can help. I have done a simmilar thing as the above. I used it to find duplicates based on several collumns by adding count* > 1. But now i want to show rows that are in these groups. How can I do that? | | khan150 | 21-09-2011 |
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Floris,
suppose you are trying to find dup records in the table above. This should help
SELECT d_id, count(d_id) as numofoccurrence
FROM documents
GROUP BY d_id
HAVING count(d_id) > 1
this will display the d_id of the record and number of times its repeating. if you want to see the entire record, add more columns after select and group by respectively | | Ambas | 02-03-2013 |
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if can want to ask, i have 2 tables, in the have the same name of field and how i can call form text data to the combobox with php? thanks.
| | smo123 | 11-04-2013 |
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Along with table name you can call the columns like this.
select table1.name1, table2.name1 from table1, table2 where table1.id=table2.id
Here both tables have same column name name1 and id |
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