postgresql行转列与列转行图文教程

2023-06-11 10:39

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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

postgresql行转列与列转行图文教程

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

postgresql行转列与列转行图文教程

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

pgsql官方对functions-array的解释

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)

可以参考pgsql官方的tablefunc实用说明

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）