oracle merge field, column to row, row to column operation

1. Merge fields

Principle: Use wm_concat function, group by grouping function to complete

1. Create a test table

create table test_concat
(
ID     VARCHAR2(10),
NAME   VARCHAR2(20),
TYPE  VARCHAR2(10)
)

2. Initialize the test data

ID NAME TYPE

1 jia 70

2 jia 75

3 jia 80

4 yi 75

5 yi 79

6 yi 88

3. Execute sql

select name,wm_concat(type) type_all from test_concat group by name;

4. Execution results

NAME TYPE_ALL

Jia 70,75,80

yi 75,79,88

5. After this execution, there will be duplicate data, which needs to be deduplicated.

Two, row to column

Principle: Use the sum focus function, the decode judgment function, and the group by grouping function to complete the synthesis.
Note: The sum function can focus not only on the numeric type of number, but also on the non-numeric varchar2 type.
1. Create a test data table: test

create table test
(
ID     VARCHAR2(10),
NAME   VARCHAR2(20),
COURSE VARCHAR2(20),
SCORE  NUMBER
)

2. Initialize the test data:

ID NAME COURSE SCORE

1 jia Chinese 70

2 jia Math 75

3 jia English 80

4 yi Chinese 75

5 yi Math 79

6 yi English 88

3. Execute sql

select name,
sum(decode(course,'Chinese',score,null)) Chinese,
sum(decode(course,'Math',score,null)) Math,
sum(decode(course,'English',score,null)) English
from test
group by name
order by name;

Or replace the judgment function decode with case when executing sql

select name,
sum(case course when 'Chinese' then score else null end) Chinese,
sum(case course when 'Math' then score else null end) Math,
sum(case course when 'English' then score else null end) English
from test
group by name
order by name;

4. Execution result:

NAME CHINESE MATH ENGLISH

Jia 70 75 80

yi 75 79 88

Three, row to column

Principle: use the union function

1. Create a test table

create table TEST_NEW
(
ID       VARCHAR2(10),
NAME     VARCHAR2(20),
CHINESE  VARCHAR2(10),
ENGLISH  VARCHAR2(10),
MATH     VARCHAR2(10)
)

2. Initialize the test data

ID NAME CHINESE ENGLISH MATH

1 jia 70 75 80

2 yi 76 73 88

3. Execute sql

select NAME, 'CHINESE' COURSE , CHINESE as SCORE from test_new
union
select NAME, 'MATH' COURSE, MATH as SCORE from test_new
union
select NAME, 'ENGLISH' COURSE, ENGLISH as SCORE from test_new
order by NAME,COURSE

4. Execution results

NAME COURSE SCORE

jia Chinese 70

jia Math 75

jia English 80

yi Chinese 76

yi Math 73

yi English 88

oracle merge field, column to row, row to column operation

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