PostgreSQL 行变列的小应用

好久没写博客了 也好久没写代码了 拿这个充充数吧 哈哈

今天在群里看到一朋友提问

问题是截图，截图如下

用Postgresql的crosstab很快就能做出来

CREATE TABLE sales
(
  year integer,-- 年
  month integer,-- 月
  counts integer -- 日
)
WITH (
  OIDS=FALSE
);
ALTER TABLE sales
  OWNER TO postgres;
COMMENT ON TABLE sales
  IS '销售报表';
COMMENT ON COLUMN sales.year IS '年';
COMMENT ON COLUMN sales.month IS '月';
COMMENT ON COLUMN sales.counts IS '日';

insert into sales values(1991,1,11),(1991,2,12),3,13),4,14),(1992,21),22),23),24);

CREATE EXTENSION tablefunc;

select * from sales;

SELECT * FROM crosstab('select year,month,counts from sales order by 1','select distinct month from sales order by 1') AS t ("年" integer,"一月" integer,"二月" integer,"三月" integer,"四月" integer);

另外需要注意下crosstab这个EXTENSION需要create才可以用。


结果如下截图