postgresql行转列与列转行图文教程
作者:Moshow郑锴
PostgreSQL是一种开源的关系型数据库,它提供了多种管理工具来操作数据库,下面这篇文章主要给大家介绍了关于postgresql行转列与列转行的相关资料,文中通过实例代码介绍的非常详细,需要的朋友可以参考下
列转行
postgresql列转行的思路主要是利用string_to_array
进行数组转换,然后用unnest
进行行拆分
select t.bid_unit,unit_id from unit t where t.unit_id=1947; result=> 中国信息通信研究院;北京市海淀区学院 -- by zhengkai.blog.csdn.net
select unnest(string_to_array(t.bid_unit,';')),unit_id from unit t where t.unit_id=1947; result=> 中国信息通信研究院 北京市海淀区学院 -- by zhengkai.blog.csdn.net
Function | Return Type | Description | Example | Result |
---|---|---|---|---|
string_to_array(text, text [, text]) | text[] | splits string into array elements using supplied delimiter and optional null string (使用提供的分隔符和可选的空字符串将字符串分割为数组元素) | string_to_array(‘xx^yy^zz’, ‘^’, ‘yy’) | {xx,NULL,zz} |
unnest(anyarray) | setof anyelement | expand an array to a set of rows(将数组展开到一组行) | unnest(ARRAY[1,2]) | 1 2 (2 rows) |
行转列
用postgresql的crosstab
交叉函数
-- by zhengkai.blog.csdn.net create table sales(year int, month int, qty int); insert into sales values(2022, 1, 1000); insert into sales values(2022, 2, 1500); insert into sales values(2022, 7, 500); insert into sales values(2022, 11, 1500); insert into sales values(2022, 12, 2000); insert into sales values(2023, 1, 1200); select * from crosstab( 'select year, month, qty from sales order by 1', 'select m from generate_series(1,12) m' ) as ( year int, "Jan" int, "Feb" int, "Mar" int, "Apr" int, "May" int, "Jun" int, "Jul" int, "Aug" int, "Sep" int, "Oct" int, "Nov" int, "Dec" int ); year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec ------+------+------+-----+-----+-----+-----+-----+-----+-----+-----+------+------ 2022 | 1000 | 1500 | | | | | 500 | | | | 1500 | 2000 2023 | 1200 | | | | | | | | | | | (2 rows)
Function | Returns | Description |
---|---|---|
normal_rand(int numvals, float8 mean, float8 stddev) | setof float8 | Produces a set of normally distributed random values(产生一组正态分布的随机值) |
crosstab(text sql) | setof record | Produces a “pivot table” containing row names plus N value columns, where N is determined by the row type specified in the calling query(生成一个包含行名和N个值列的“数据透视表”,其中N个由调用查询中指定的行类型决定) |
crosstabN(text sql) | setof table_crosstab_N | Produces a “pivot table” containing row names plus N value columns. crosstab2, crosstab3, and crosstab4 are predefined, but you can create additional crosstabN functions as described below(生成一个包含行名和N个值列的“数据透视表”。交叉表2、交叉表3和交叉表4都是预定义的,但是您可以创建额外的跨表n函数,如下面所述) |
crosstab(text source_sql, text category_sql) | setof record | Produces a “pivot table” with the value columns specified by a second query(生成具有由第二个查询指定的值列的“数据透视表”) |
crosstab(text sql, int N) | setof record | Obsolete version of crosstab(text). The parameter N is now ignored, since the number of value columns is always determined by the calling query(过时版本的交叉表(文本)。参数N现在被忽略,因为值列的数量总是由调用查询决定) |
connectby(text relname, text keyid_fld, text parent_keyid_fld [, text orderby_fld ], text start_with, int max_depth [, text branch_delim ]) | setof record | Produces a representation of a hierarchical tree structure(生成层次树结构的表示) |
总结
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