postgresql – 当串联两列时,如何在字符串agg中添加顺序

概述SELECT string_agg( distinct a || '-' || b , ',' ORDER BY a,b) FROM table; 上面的sql给出了错误 ERROR: in an aggregate with DISTINCT, ORDER BY expressions must appear in argument list 对于 the documentation： If @H_403_7@SELECT string_agg( distinct a || '-' || b,',' ORDER BY a,b) FROM table;

上面的sql给出了错误

ERROR: in an aggregate with disTINCT,ORDER BY Expressions must appear in argument List

解决方法 对于 the documentation：

If disTINCT is specifIEd in addition to an order_by_clause,then all the ORDER BY Expressions must match regular arguments of the aggregate; that is,you cannot sort on an Expression that is not included in the disTINCT List.

所以试试吧

@H_403_7@select string_agg(distinct a || '-' || b,' order by a || '-' || b)from a_table;

或在派生表中使用distinct：

@H_403_7@select string_agg(a || '-' || b,' order by a,b)from ( select distinct a,b from a_table ) s; 总结

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