问题
Well I have this records:
Employee_Number Employee_role Group_Name
----------------------------------------------------
EMP101 C# Developer Group_1
EMP102 ASP Developer Group_1
EMP103 SQL Developer Group_2
EMP104 PLSQL Developer Group_2
EMP101 Java Developer
EMP102 Web Developer
EMP101 DBA
EMP105 DBA
EMP106 SQL Developer Group_3
EMP107 Oracle Developer Group_3
EMP101 Oracle Developer Group_3
Want to show the pivot table for above records in the following format:
Employee_Number TotalRoles TotalGroups Available Others Group_1 Group_2 Group_3
-----------------------------------------------------------------------------------------------------------------
EMP101 4 3 2 2 1 1
EMP102 2 3 1 1 1
EMP103 1 3 1 0 1
EMP104 1 3 1 0 1
EMP105 1 3 0 1
EMP106 1 3 1 0 1
EMP107 1 3 1 0 1
For the above result I am using the following script:
SELECT * FROM crosstab(
$$SELECT grp.*, e.group_name
, CASE WHEN e.employee_number IS NULL THEN 0 ELSE 1 END AS val
FROM (
SELECT employee_number
, count(employee_role)::int AS total_roles
, (SELECT count(DISTINCT group_name)::int
FROM employee
WHERE group_name <> '') AS total_groups
, count(group_name <> '' OR NULL)::INT AS available
, count(group_name = '' OR NULL)::int AS others
FROM employee
GROUP BY employee_number
) grp
LEFT JOIN employee e ON e.employee_number = grp.employee_number
AND e.group_name <> ''
ORDER BY grp.employee_number, e.group_name$$
,$$VALUES ('Group_1'),('Group_2'),('Group_3')$$
) AS ct (employee_number text
, total_roles int
, total_groups int
, available int
, others int
, "Group_1" int
, "Group_2" int
, "Group_3" int);
But:Now I want to show the pivot table for the above records by filtering the Group_Name.
That means if I want to show the pivot table for the only Group_Name= Group_3 then it has
to show only the employee who is only belongs to the Group_Name= Group_3 not other than that.
If I want to see the employee who is belongs to the Group_3 only than it has to show me:
Employee_Number total_roles total_groups available others Group_3
-------------------------------------------------------------------------------
EMP106 1 3 1 0 1
EMP107 1 3 1 0 1
Note: As you can see in the first table the employee EMP106 and EMP107 is only belongs
to the Group_Name = Group_3. The employee EMP101 is also belong but he also belongs to other groups
so should not appear in this table.
回答1:
How to exclude the offending rows:
- Select rows which are not present in other table
The crosstab() version adapted:
SELECT * FROM crosstab(
$$SELECT grp.*, e.group_name
, CASE WHEN e.employee_number IS NULL THEN 0 ELSE 1 END AS val
FROM (
SELECT employee_number
, count(employee_role)::int AS total_roles
, (SELECT count(DISTINCT group_name)::int
FROM employee
WHERE group_name <> '') AS total_groups
, count(group_name <> '' OR NULL)::int AS available
, count(group_name = '' OR NULL)::int AS others
FROM employee
GROUP BY employee_number
) grp
JOIN employee e USING (employee_number)
WHERE e.group_name = 'Group_3'
AND NOT EXISTS (
SELECT 1 FROM employee
WHERE employee_number = e.employee_number
AND group_name e.group_name
)
ORDER BY employee_number$$
,$$VALUES ('Group_3')$$
) AS ct (employee_number text
, total_roles int
, total_groups int
, available int
, others int
, "Group_3" int);But as you can see, we don't need crosstab() here at all. Simplify to:
SELECT grp.*, 1 AS "Group_3"
FROM (
SELECT employee_number
, count(employee_role)::int AS total_roles
, (SELECT count(DISTINCT group_name)::int
FROM employee
WHERE group_name <> '') AS total_groups
, count(group_name <> '' OR NULL)::int AS available
, count(group_name = '' OR NULL)::int AS others
FROM employee
GROUP BY employee_number
) grp
JOIN employee e USING (employee_number)
WHERE e.group_name = 'Group_3'
AND NOT EXISTS (
SELECT 1 FROM employee
WHERE employee_number = e.employee_number
AND group_name <> e.group_name
)
ORDER BY employee_number;
The column "Group_3" is really just noise here, because it is always 1 by definition.
If only a small percentage of rows is selected this way, this version with a LATERAL join should be substantially faster:
SELECT e.employee_number
, grp.total_roles
, total.total_groups
, grp.available
, grp.others
, 1 AS "Group_3"
FROM (
SELECT employee_number
FROM employee e
WHERE group_name = 'Group_3'
AND NOT EXISTS (
SELECT 1 FROM employee
WHERE employee_number = e.employee_number
AND group_name <> e.group_name
)
) e
, LATERAL (
SELECT count(employee_role)::int AS total_roles
, count(group_name <> '' OR NULL)::int AS available
, count(group_name = '' OR NULL)::int AS others
FROM employee
WHERE employee_number = e.employee_number
GROUP BY employee_number
) grp
, (
SELECT count(DISTINCT group_name)::int AS total_groups
FROM employee
WHERE group_name <> ''
) total
ORDER BY employee_number;
Details for the LATERAL solution and performance:
- Optimize GROUP BY query to retrieve latest record per user
Simple, generic solution for any set of groups
Not optimized for performance, but easy to adapt:
<original crosstab query from your question>
WHERE "Group_3" = 1
AND "Group_1" IS NULL
AND "Group_2" IS NULL
AND "Group_4" IS NULL
AND others = 0 -- to rule out membership in the "empty" group
-- possibly more ...
来源：https://stackoverflow.com/questions/29145696/postgresql-9-3-filter-in-pivot-table-query