问题
I am having a table with many columns (but posting only col1, col2, col3 here for simplified post):
id col1 col2 col3 source_id
a1 765.3 23-Apr-08 cat a5
a2 3298.3 (null) dog a4
a3 8762.1 27-Nov-10 rat a8
a4 (null) (null) (null) (null)
a5 (null) (null) (null) a6
a6 (null) (null) (null) (null)
I want to fill null values of source _id
with values from id
.
For example, source_id a5 row has null
which has to replaced with id a1 values
, subsequently, source_id a6 row having null
to be replaced with a5 row
Output:
id col1 col2 col3 source_id
a1 765.3 23-Apr-08 cat a5
a2 3298.3 (null) dog a4
a3 8762.1 27-Nov-10 rat a8
a4 3298.3 (null) dog (null)
a5 765.3 23-Apr-08 cat a6
a6 765.3 23-Apr-08 cat (null)
回答1:
This looks like a left join
and conditional logic:
select
t.id,
coalesce(t.col1, t1.col1) col1,
coalesce(t.col2, t1.col2) col2,
coalesce(t.col3, t1.col3) col3,
t.source_id
from mytable t
left join mytable t1 on t1.id = t.source_id
来源:https://stackoverflow.com/questions/62061075/replacing-null-based-on-a-condition