Sql – Oracle SQL query count, group by with an innerjoin

countoraclesql

Basicly I have a bunch of Cars that belong to dealers and the dealers have a group.
The dealer table has the GROUP.ID and the Group table has the group name.
A Group has multiple dealers

So I want to count how many cars each group has.

I am using this atm

select  
  (select GROUP_NAME from "GROUP" where "GROUP".GROUP_ID = "DEALER"."GROUP_ID" ),
  "DEALER"."GROUP_ID" as "DEALER GROUP ID",
  "DEALER"."DEALER_NAME" as "DEALER DEALER NAME",
  "CAR"."CAR_DEALER" as "CAR DEALER"         
from 
  "CAR"
INNER JOIN 
  DEALER
ON 
  "DEALER"."DEALER_NAME" ="CAR"."CAR_DEALER"

I tried using group_by and count but I can't seem to get it to work

Best Answer

select
  g.GROUP_NAME,
  g.GROUP_ID,
  count(*) as CAR_COUNT
from
  GROUP g
  inner join DEALER d on d.GROUP_ID = g.GROUP_ID
  inner join CAR c on c.DEALER_ID = d.DEALERID
group by
  /* Also add here all field you want to select from GROUP */
  g.GROUP_NAME,
  g.GROUPID

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to limit the number of rows returned by an Oracle query after ordering

You can use a subquery for this like

select *
from  
( select * 
  from emp 
  order by sal desc ) 
where ROWNUM <= 5;

Have also a look at the topic On ROWNUM and limiting results at Oracle/AskTom for more information.

Update: To limit the result with both lower and upper bounds things get a bit more bloated with

select * from 
( select a.*, ROWNUM rnum from 
  ( <your_query_goes_here, with order by> ) a 
  where ROWNUM <= :MAX_ROW_TO_FETCH )
where rnum  >= :MIN_ROW_TO_FETCH;

(Copied from specified AskTom-article)

Update 2: Starting with Oracle 12c (12.1) there is a syntax available to limit rows or start at offsets.

SELECT * 
FROM   sometable
ORDER BY name
OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;

See this answer for more examples. Thanks to Krumia for the hint.

Best Answer

Related Solutions

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to limit the number of rows returned by an Oracle query after ordering

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