group by where code example

Example 1: sql group by

# Say you have a table called SALARIES that contains a 
# few duplicate NAME entries...
+----+-------------+--------+
| ID |    NAME     | SALARY |
+----+-------------+--------+
| 1	 |     Bob     |  500   |
| 2  |    Alice    |  500   |
| 3  |    Alice    |  200   |
| 4  |    Frank    |  700   |
| 5  |    Percy    |  100   |
| 6  |    Percy    |  800   |
| 7  |   Cyrille   |  400   |
+----+-------------+--------+

# We can obtain the total salaries of each person
# by using GROUP BY in the following query...
SELECT NAME, SALARY FROM SALARIES GROUP BY NAME;

# Which will output the following...
+------------+--------+
|   Alice    |  700   |
|    Bob     |  500   |
|  Cyrille   |  400   |
|   Frank    |  700   |
|   Percy    |  900   |
+------------+--------+

Example 2: MySQL GROUP BY

SELECT 
    c1, c2,..., cn, aggregate_function(ci)
FROM
    table
WHERE
    where_conditions
GROUP BY c1 , c2,...,cn;

Example 3: group by in sql

GROUP BY: is used to collaborate
with the SELECT statement to arrange 
matching data into groups.

ORDER BY: is for sorting result
either in descending or ascending order.

Example 4: groupby where only

>>> df = pd.DataFrame({'A' : ['foo', 'bar', 'foo', 'bar',
...                           'foo', 'bar'],
...                    'B' : [1, 2, 3, 4, 5, 6],
...                    'C' : [2.0, 5., 8., 1., 2., 9.]})
>>> grouped = df.groupby('A')
>>> grouped.filter(lambda x: x['B'].mean() > 3.)
     A  B    C
1  bar  2  5.0
3  bar  4  1.0
5  bar  6  9.0

Example 5: GROUP BY

SELECT <field1, field2, field3…>
FROM <table1_name>
WHERE <condition/expression>
GROUP BY <field1, field2, field3…>

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