问题
I'm not quite sure why this table was designed this way, but it's making it hard to solve my problem. Looking at the data:
NAME TYPE_NAME DEFAULT_VALUE VALUE
TEST 1 Currency Null 14
TEST 1 Event Count 0 0
TEST 1 Usage 8 Null
TEST 1 Events Amt 0 0
TEST 1 Usage Amt Null 13
TEST 1 From Date Null 5
TEST 1 To Date 6 Null
TEST 1 Traffic Scenario Null 2
TEST 1 Band 1 Null
TEST 1 Service 15 Null
TEST 1 Tariff Rate Name Null 4
TEST 2 Currency EUR 0
TEST 2 Event Count Null 9
TEST 2 Usage 10 Null
TEST 2 Events Amt Null 13
TEST 2 Usage Amt Null 14
TEST 2 From Date Null 3
TEST 2 To Date 4 Null
TEST 2 Traffic Scenario Null 5
TEST 2 Band 6 Null
TEST 2 Service 7 Null
TEST 2 Tariff Rate Name Null 8
TEST 3 Currency USD 0
TEST 3 Event Count 0 0
TEST 3 Usage 4 Null
TEST 3 Events Amt 0 0
TEST 3 Usage Amt Null 5
TEST 3 From Date Null 1
TEST 3 To Date 2 Null
TEST 3 Traffic Scenario 13603 0
TEST 3 Band 3 Null
TEST 3 Service 3 Null
TEST 3 Tariff Rate Name 24HR 0
What I need help with is to do the following: For each name have the type_name as a column and then fill those columns with the default_value or value.
Like this:
NAME Currency Event Count Usage Events Amt Usage Amt From Date To Date Traffic Scenario Band Service Tariff Rate Name
TEST 1 14 0 8 0 13 5 6 2 1 15 4
TEST 2 EUR 9 10 13 14 3 4 5 6 7 8
TEST 3 USD 0 4 0 5 1 2 13603 3 3 24HR
Basically populates from default_value or value depending which one is not null, if both zero then just 0.
Could anyone help me with this as my SQL knowledge is lacking here.
Many thanks!
回答1:
You can use PIVOT as follows:
SELECT * FROM
( SELECT NAME, TYPE_NAME, COALESCE(VALUE, DEFAULT_VALUE) AS VAL
FROM YOUR_TABLE
)
PIVOT
( MAX ( VAL )
FOR TYPE_NAME IN ( 'Currency' AS CURRENCY, 'Event Count' AS EVENT_COUNT,
'Usage' AS USAGE_, 'Events Amt' AS EVENTS_AMT )
)
Cheers!!
回答2:
This is an EAV (entity-attribute-value) table. If you know the columns you want, you can use conditional aggregation:
select name,
max(case when type_name = 'Currency' then default_value end) as currency,
max(case when type_name = 'Event Count ' then default_value end) as EventCount,
. . .
from t
group by name;
If you don't know all the types, then you need dynamic SQL -- that is, PL/SQL in Oracle.
回答3:
You can do conditional aggregation:
select
name,
max(case when type_name = 'Currency'
then coalesce(value, default_value)
end) currency,
max(case when type_name = 'Event Count'
then coalesce(value, default_value)
end) event_count,
max(case when type_name = 'Usage'
then coalesce(value, default_value)
end ) usage,
max(case when type_name = 'Events Amt'
then coalesce(value, default_value)
end) events_amt
from mytable
group by name
The conditional expressions actually pivots the resulset; coalesce() returns either value, if it is not null, or default_value.
回答4:
You can try it. I tried on oracle.
Also this method COALESCE (DEFAULT_VALUE, VALUE) needs to control first DEFAULT_VALUE and second VALUE.
SELECT t1.NAME,
max(CASE WHEN t1.TYPE_NAME ='Currency' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS Currency,
max(CASE WHEN t1.TYPE_NAME ='Event Count' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS Event_Count
max(CASE WHEN t1.TYPE_NAME ='Usage' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS Usage,
max(CASE WHEN t1.TYPE_NAME ='Usage Amt' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS Usage_Amt,
max(CASE WHEN t1.TYPE_NAME ='From Date' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS From_Date,
max(CASE WHEN t1.TYPE_NAME ='Band' THEN COALESCE (t1.DEFAULT_VALUE, T1.VALUE) END) AS Band,
.......
......
FROM MYTABLE t1 GROUP BY t1.NAME
来源：https://stackoverflow.com/questions/60670251/sql-turning-rows-into-columns-and-populating-with-values