I Have oracle table with data as shown below.
column1 column2
A1 B1
B1 C1
C1 D1
I need to get A1 value from D1. I have to implemet this in View. Need to traverse using as D1 as input and get C1 and get B1 from C1 and finally A1 using B1
Please help.
Not sure what kind of view you are looking to create; if you are thinking of passing 'A1' as an input to the view, there is no such thing in Oracle as far as I know, you would need to use a cursor for that.
The following SELECT statement can be used as an inline view (a subquery) and you can make the 'D1' value at the end of it into a bind variable if needed.
select column1
from test_data
where connect_by_isleaf = 1
connect by column2 = prior column1
start with column2 = 'D1'
;
Related
Apache Hive (version 1.2.1000.2.6.5.0-292)
I have a table, A, that has a large number of columns. I'm trying to select only the columns that I need from A and the columns I want live in a key-value pair table, B. (Example below). I can query B to get the columns I need, but I'm struggling to put the output of this sql query as the columns of the query used in A. Is there a way to do this in one sql query? I can write a python program to do this to create the SQL, but I'd rather have it in just one query for simplicity to the end-user.
DDL for tables
create table A (
a1 string,
a2 string,
a3 string,
b1 string,
b2 string,
b3 string,
)
create table B (
key string,
value string,
)
Data in table B (key value table). It should be noted that the data in the column value cannot be inferred upon by the corresponding value in column key. I have written them as a1,a2 for simplicity.
key,value
a,a1
a,a2
a,a3
b,b1
b,b2
b,b3
Query to get the correct columns = select value from B where key='a'
When you merge the results from this query with the Table A query you should get this sql statement
select a1,a2,a3 from A
As you can see, we are trying to derive the columns used in Table A
My first attempt doesn't work:
select
(select value from B where key='a')
from A
What's the right way to do this?
Thanks in advance!
You can try to generate query and write to file. Once done, you can call in existing hive hql using source command:
Here is sample queries by taking your example:
Create table and dummy data:
CREATE EXTERNAL TABLE IF NOT EXISTS a_table(
a1 string,
a2 string,
a3 string,
b1 string,
b2 string,
b3 string)
LOCATION '/user/xyz/a_table';
insert into table a_table
VALUES ('a11', 'a12', 'a13','b11','b12','b13'), ('a21', 'a22', 'a23','b21','b22','b23');
CREATE EXTERNAL TABLE IF NOT EXISTS b_table (
key string,
value string
)
LOCATION '/user/xyz/b_table';
insert into table b_table
VALUES ('a', 'a1'), ('a','a2'),('a','a3'), ('b', 'b1'), ('b','b2'),('b','b3');
Validate data into table:
select * from a_table;
OK
a11 a12 a13 b11 b12 b13
a21 a22 a23 b21 b22 b23
Time taken: 0.124 seconds, Fetched: 2 row(s)
select * from b_table;
OK
a a1
a a2
a a3
b b1
b b2
b b3
Time taken: 0.15 seconds, Fetched: 6 row(s)
This is hive hql part to generate statement based on given key and then using source to run query:
insert overwrite local directory '/home/xyz/temp_hql/out'
select concat_ws(" ", "select",concat_ws("," , collect_list(value)), "from a_table")
from b_table where key = 'a';
source /home/xyz/temp_hql/out/000000_0;
OK
a11 a12 a13
a21 a22 a23
insert overwrite local directory '/home/xyz/temp_hql/out'
select concat_ws(" ", "select",concat_ws("," , collect_list(value)), "from a_table")
from b_table where key = 'b';
source /home/xyz/temp_hql/out/000000_0;
OK
b11 b12 b13
b21 b22 b23
I am new to hive. Please help with my below problem.
I have below table in hive with one column having data with | as delimeter.
C1
1|2|3|4|5|6
7||9|10|11|12
The below one is expected output based on delimeter i want to split it as columns.
C1 C2 C3 C4 C5 C6
1 2 3 4 5 6
7 9 10 11 12
I have tried with locate and substr functions and endup with complex sql query. can you people help me in a simple way to do this.
Thank you!
Use split which returns an array of values from which individual elements can be selected as columns.
select split(c1,'\\|')[0] as c1
,split(c1,'\\|')[1] as c2
,split(c1,'\\|')[2] as c3
,split(c1,'\\|')[3] as c4
,split(c1,'\\|')[4] as c5
,split(c1,'\\|')[5] as c6
from tbl
code
select c1,c2,c3,c4,c5,c6
from table
where c5 in ('a', 'b')
From here, I want to split column c5 into two columns and then rank those based on the value they have for c6. One column should be made up of all a results, and the other should be all b results. I have been able to rank them using rank() over, but have been unable to split the columns apart. I haven't gotten the techniques other people have used to work for me.
select c1,c2,c3,c4,c5,c6, rank() over (partition by ... order by case when c5='a' then 1 case when c5='b' then 2 end) as rnk;
I do not understand completely what c5 contains exactly. Replace conditions like when c5='a' in case with yours.
I have a table a
c1 c2 c3 c4 value
all all all all 5
all david all Y 6
all all cd all 7
and table b
c1 c2 c3 c4
a peter cd N
b david all Y
c all cd N
I want to have get the value from table a into table b, the desired results is like this:
c1 c2 c3 c4 Value
a david cd N 5
b david ab Y 6
c all cd N 7
That is use the default "all" value if there is no close match find.
Thanks a lot!
I see a couple of possibilities assuming you have some errors in your example result data. (C2 for value 5 and C3 for value 6 are suspect to me)
Use a CTE to union the results replace all with null and use aggregation to get max value
Use a Join on value and evaluate table a's value for each c column if it's not all use it, otherwise use B's value. (IF a and b are both all it doesn't matter which we use.) this may be problematic if both values are potentially different like if Value 6 had a Y in A, and a N in B. but no such example exits in your data so I'm trusting it doesn't happen. (or if it did, picking A's value is more appropriate if it's not all)
AS a cte: (Common Table expression)
WITH cte as (
SELECT replace(c1,'all',null)
, replace(c2,'all',null)
, replace(c3,'all',null)
, replace(c4,'all',null)
, value
FROM A
UNION ALL
SELECT replace(c1,'all',null)
, replace(c2,'all',null)
, replace(c3,'all',null)
, replace(c4,'all',null)
, value
FROM b)
/* We have to eval the max as if it's null we need to replace it with all
Might be able to avoid the replacing all provided all values of c1-c4 are
greater than all... replacing just seemed safer. at a hit to performance.*/
SELECT coalesce(max(c1),'all') as c1
,coalesce(max(c2),'all') as c2
,coalesce(max(c3),'all') as c3
,coalesce(max(c4),'all') as c4
,value
FROM cte
GROUP BY value
Using a join (simpler from a maintenance and perhaps performance standpoint)
SELECT case when A.C1 <> 'all' then A.C1 else B.c1 end as C1,
case when A.C2 <> 'all' then A.C2 else B.c2 end as C2,
case when A.C3 <> 'all' then A.C3 else B.c3 end as C3,
case when A.C4 <> 'all' then A.C4 else B.C4 end as C4,
A.value --A.val = b.val so it doesn't matter which se use.
FROM A
INNER JOIN B
on A.value = B.Value
Depending on existing indexes and data volume the first approach might be better than the second.
Can I cast B1 char(2) which joins on A1 varchar2(2) :
SELECT * FROM A
LEFT JOIN B
ON CAST(B.B1 AS VARCHAR2(2)) = A.A1
It results to no errors, but there no data displayed.
Is the above query possible?
You can cast it, but it isn't doing that you think, or seem to be relying on. Assuming you have a one-character value in the field you're joining on, you don't get a match, with or without the cast:
create table a (a1 varchar2(2));
create table b (b1 char(2));
insert into a values ('X');
insert into b values ('X');
select * from a left join b on b.b1 = a.a1;
A1 B1
-- --
X
select * from a left join b on cast(b.b1 as varchar2(2)) = a.a1;
A1 B1
-- --
X
The cast is chaging the data type, but not the data; it is still blank-padded. The only difference is that it's done explicitly in the value, rather implicitly as you'd see with a char. You can verify that the value is the same with the dump() function:
select dump(b.b1) dump_char,
dump(cast(b.b1 as varchar2(2))) dump_varchar2
from b;
DUMP_CHAR DUMP_VARCHAR2
-------------------- --------------------
Typ=96 Len=2: 88,32 Typ=1 Len=2: 88,32
So the type has changed, from 96 (char) to 1 (varchar2), but the value is the same. Compare that with your value in table A and you'll see they are not the same:
select dump(a.a1) dump_varchar2 from a;
DUMP_VARCHAR2
--------------------
Typ=1 Len=1: 88
Your cast B value still has the trailing space, the A value does not, therefore they don't match. You can remove that trailing space for comparison with trim() or rtrim():
select * from a left join b on rtrim(b.b1) = a.a1;
A1 B1
-- --
X X
There is an implicit conversion from char to varchar2 within the rtrim() call, so you could still cast that explicitly for clarity.
Note that this assumes you never have a trailing space in A. It may be safer to cast the other way:
select * from a left join b on b.b1 = cast(a.a1 as char(2));
A1 B1
-- --
X X
... but which side you cast/trim will also affect which indexes can be used.
this worked for me:
SELECT * FROM A
LEFT JOIN B
ON TRIM(B.B1) = A.A1
i prefer this syntax to the cast for purely aesthetic reasons, although presumably others exist