convert lines into single row [duplicate] - sql

Question

This question already has answers here:
Dynamic Pivot in Oracle's SQL
(10 answers)
Closed 10 months ago.
I have data like this
Col1 Col 2
100 1
100 2
100 3
100 4
need output like this
Col1 col2 col3 col4 col5
100 1 2 3 4
need to define as new col names and populate values into these fields.

Answer 1

If you have a fixed maximum number of input rows/output columns you can use:
SELECT *
FROM table_name
PIVOT (
MAX(Col2)
FOR Col2 IN (1 AS col2, 2 AS col3, 3 AS col4, 4 AS col5)
)
Which, for the sample data:
CREATE TABLE table_name (Col1, Col2) AS
SELECT 100, 1 FROM DUAL UNION ALL
SELECT 100, 2 FROM DUAL UNION ALL
SELECT 100, 3 FROM DUAL UNION ALL
SELECT 100, 4 FROM DUAL;
Outputs:
COL1
COL2
COL3
COL4
COL5
100
1
2
3
4
If you can have a maximum of 15 rows then:
SELECT *
FROM (
SELECT t.*, ROW_NUMBER() OVER (PARTITION BY Col1 ORDER BY Col2) AS rn
FROM table_name t
)
PIVOT (
MAX(Col2)
FOR rn IN (
1 AS col2,
2 AS col3,
3 AS col4,
4 AS col5,
5 AS col6,
6 AS col7,
7 AS col8,
8 AS col9,
9 AS col10,
10 AS col11,
11 AS col12,
12 AS col13,
13 AS col14,
14 AS col15,
15 AS col16
)
)
or:
SELECT Col1,
MAX(CASE rn WHEN 1 THEN Col2 END) AS Col2,
MAX(CASE rn WHEN 2 THEN Col2 END) AS Col3,
MAX(CASE rn WHEN 3 THEN Col2 END) AS Col4,
MAX(CASE rn WHEN 4 THEN Col2 END) AS Col5,
MAX(CASE rn WHEN 5 THEN Col2 END) AS Col6,
MAX(CASE rn WHEN 6 THEN Col2 END) AS Col7,
MAX(CASE rn WHEN 7 THEN Col2 END) AS Col8,
MAX(CASE rn WHEN 8 THEN Col2 END) AS Col9,
MAX(CASE rn WHEN 9 THEN Col2 END) AS Col10,
MAX(CASE rn WHEN 10 THEN Col2 END) AS Col11,
MAX(CASE rn WHEN 11 THEN Col2 END) AS Col12,
MAX(CASE rn WHEN 12 THEN Col2 END) AS Col13,
MAX(CASE rn WHEN 13 THEN Col2 END) AS Col14,
MAX(CASE rn WHEN 14 THEN Col2 END) AS Col15,
MAX(CASE rn WHEN 15 THEN Col2 END) AS Col16
FROM (
SELECT t.*, ROW_NUMBER() OVER (PARTITION BY Col1 ORDER BY Col2) AS rn
FROM table_name t
)
GROUP BY Col1
Which both output:
COL1
COL2
COL3
COL4
COL5
COL6
COL7
COL8
COL9
COL10
COL11
COL12
COL13
COL14
COL15
COL16
100
1
2
3
4
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
db<>fiddle here

Answer 2

There is 1 more way, called Conditional aggregation to achieve the same result -
SELECT Col1,
MAX(CASE WHEN Col2 = 1 THEN Col2 END) Col2,
MAX(CASE WHEN Col2 = 2 THEN Col2 END) Col3,
MAX(CASE WHEN Col2 = 3 THEN Col2 END) Col4,
MAX(CASE WHEN Col2 = 4 THEN Col2 END) Col5
FROM table_name
GROUP BY Col1;
If you have 15 values, You have to pass them manually in both the queries and your result will always have 15 columns. If you want to have them dynamically transformed, refer the answer in original comment.