Display record even if it doesn't exist

问题

So I have this table

Col1    Col2    Col3
A       34       X
B       43       L
A       36       L

Now if I query

select * from Table1 where col1 in ('A','B','C')

I am expecting something like

Col1    Col2    Col3
A       34       X
B       43       L
A       36       L
C       -        -

Is it possible ?

P.S: the - in row C are just to show that the column is empty.

回答1:

You could create a nested table schema object type:

create type T_List1 as table of varchar2(100);

And then construct your query as follows:

 select s.column_value            as col1
      , nvl(to_char(t.col2), '-') as col2
      , nvl(col3, '-')            as col3
  from Table1 t
 right join table(T_List1('A', 'B', 'C')) s
    on (t.col1 = s.column_value)

Example:

-- sample of data from your question
with Table1(Col1, Col2, Col3) as(
  select 'A',  34,  'X' from dual union all
  select 'B',  43,  'L' from dual union all
  select 'A',  36,  'L' from dual
)  -- actual query
 select s.column_value            as col1
      , nvl(to_char(t.col2), '-') as col2
      , nvl(col3, '-')            as col3
   from Table1 t
  right join table(T_List1('A', 'B', 'C')) s --< here list your values
     on (t.col1 = s.column_value)            -- as you would using `IN` clause

Result:

COL1  COL2   COL3
------------------------
A     36     L    
A     34     X    
B     43     L    
C     -      -

SQLFiddle Demo

回答2:

To do this you can use a driver table that has all the values you want returned in it ie:

col1
A
B
C
D
E

Then LEFT JOIN to your table.

SELECT * 
FROM driver d
LEFT JOIN Table1 t
 ON d.col1 = t.col1
WHERE d.col1 in ('A','B','C')

回答3:

If you don't want to create an extra nested table type as in Nicholas Krasnov's answer or don't want to create a separate temporary table with A,B,C rows then just create a driving table with with clause:

with driving_table(col) AS
(
  select 'A' from dual
  union 
  select 'B' from dual
  union
  select 'C' from dual

)
select dt.col            as col1
     , nvl(to_char(t.col2), '-') as col2
     , nvl(col3, '-')            as col3
  from Table1 t
 right join driving_table dt
  on (t.col1 = dt.col)

http://sqlfiddle.com/#!4/112ef/2

来源：https://stackoverflow.com/questions/18967133/display-record-even-if-it-doesnt-exist

标签

sql

oracle11g