The function string_agg is commonly used in SQL databases to concatenate a list of strings into a single string, separated by a specified delimiter.In PostgreSQL, string_agg is a built-in aggregate function that can be used to achieve this. To use string_agg, you need to provide a list ...
当然,string_agg(field,'分隔符');分隔符可以填写其他任意的字符,方便后期处理即可; 补充:PostgreSql 聚合函数string_agg与array_agg,类似mysql中group_concat string_agg,array_agg 这两个函数的功能大同小异,只不过合并数据的类型不同。 https://www.postgresql.org/docs/9.6/static/functions-aggregate.html array...
SQL Error [42P10]: ERROR: in an aggregate with DISTINCT, ORDER BY expressions must appear in argument list So, I could say: string_agg(distinct status,',' order by status) as list but this is not what I want: 'green' would get first, red second, yellow last... ...
CREATE OR REPLACE PROCEDURE aggregate_data AS CURSOR c IS SELECT your_column_name FROM your_table_name; v_result CLOB; v_buffer VARCHAR2(4000); -- 假设每次处理 4000 字节的数据块 BEGIN DBMS_LOB.CREATETEMPORARY(v_result, TRUE); -- 创建一个临时 CLOB FOR r IN c LOOP v_buffer := v_bu...
Conclusion TheSTRING_AGG()function in PostgreSQL, while seemingly straightforward, is versatile and powerful. By mastering both its fundamental and advanced applications, you can optimize database operations, making them both efficient and insightful. Whether for basic concatenation or intricate data aggre...
The ARRAY_AGG function is only available in the PostgreSQL database. It allows us to aggregate the values into a single array. An example is as follows: SELECT department, ARRAY_AGG(first_name) AS employees_list FROM employees GROUP BY ...
Summary: in this tutorial, you will learn how to use the PostgreSQL STRING_AGG() function to concatenate strings and place a separator between them. Introduction to PostgreSQL STRING_AGG() function The PostgreSQL STRING_AGG() function is an aggregate function that concatenates a list of strings ...
PostgreSQL string_agg string_agg 代替listagg,实现同样功能。 建表 postgres=#createtabletbl1 (gidint, valtext, tstimestampdefaultclock_timestamp());CREATETABLE 写入测试数据 postgres=#insertintotbl1values(1,'a'),(1,'b'),(1,null),(2,'test'),(2,'a""b"c'),(3,'fw');INSERT06 ...
If you do not specify this parameter, data in the database may be sorted in an appropriate way. FILTER ( WHERE filter_clause ): optional. The condition used to filter the rows whose values you want to aggregate. Return value A value of the TEXT type is returned. Examples Example 1...
最后，缺少的主要部分是通过创建一个新类来扩展PostgreSQL94Dialect来定义函数。因为这些函数不是为方言定义...