1. Description of requirements

The data operation of the oracle database is involved in the project development process; however, the data needs to be exchanged between columns. According to the information, there are three ways to achieve the exchange of rows and columns in oracle:

① Use the decode function;

②Use the case when function;

③Use the pivot function;

The easiest way to convert row and column in Oracle_oracle row and column conversion https://blog.csdn.net/xiaochenXIHUA/article/details/120409641?ops_request_misc=&request_id=cb8c473afe7c418baef1d3294c3831ea&biz_id=&utm_medium=distribute.p c_search_result.none-task-blog-2 ~blog~koosearch~default-1-120409641-null-null.268^v1^control&utm_term=%E8%A1%8C%E5%88%97&spm=1018.2226.3001.4450

2. Implementation method

I have a data table here with the following content:

2.1. Realize converting the content of the above picture into lines——decode function

select
  "name",
  max(decode("course", '语文', "score")) 语文,
  max(decode("course", '数学', "score")) 数学,
  max(decode("course", '英语', "score")) 英语,
  sum("score") 总分
from "grade"
group by "name";

2.2. Realize converting the content of the above picture into rows——case when function

select
  "name",
  max(case when "course"  = '语文' then "score" end) 语文,
  max(case when "course" = '数学' then "score" end) 数学,
  max(case when "course" = '英语' then "score" end) 英语,
  sum("score") 总分
from "grade"
  group by "name";

2.3. Realize converting the content of the above picture into rows——pivot function

The syntax of the pivot function:


pivot(聚合函数 for 列名 in(类型))

select t.* from(
(select * from 原表名称) 
pivot(
    max(需转的列名称) 
    for 需转的列名称 in(需转列对应的值1,需转列对应的值2,需转列对应的值3
     )
)t

SELECT t.*,(t.语文+t.数学+t.英语)总分 from ((SELECT "name","course","score" from "grade")pivot
(
	 max("score") 
	 for "course" in('语文' 语文,'数学' 数学,'英语' 英语)
))t ORDER BY "name";

2.4. Realize converting the content of the above picture into columns——unpivot function

The content that needs to be transferred is as follows:

The syntax of the unpivot function:

SELECT 列名称,需定义的列1名称,需定义的列2名称 from 表名称 unpivot (需定义的列2名称 for 需定义的列1名称 in(列2值1,列2值2,列2值3));

SELECT "name" 名字,course 课程,score 分数 from "grade2" unpivot (score for course in("chinese","math","english"));

SELECT 名字,course 课程,score 分数 from (
SELECT "name" 名字,"chinese" 语文,"math" 数学,"english" 英语 from "grade2") unpivot (score for course in(语文,数学,英语))

3. References

透视和逆透视 Oracle Database 11g | Oracle 中国https://www.oracle.com/cn/technical-resources/articles/database/sql-11g-pivot.html SELECT (oracle.com)https://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_10002.htm#SQLRF01702 DECODE (oracle.com)https://docs.oracle.com/cd/B28359_01/server.111/b28286/functions042.htm#SQLRF00631 CASE Expressions (oracle.com)https://docs.oracle.com/cd/B28359_01/server.111/b28286/expressions004.htm#SQLRF20037

Interchange between rows and columns in Oracle——pivot, unpivot function usage