在PostgreSQL 中,json_build_object 和array_agg 是两个非常有用的函数,它们可以用来构建 JSON 对象和处理数组。然而,distinct 关键字不能直接与 array_agg 函数一起使用,因为 array_agg 默认会聚合所有行中的值,而不考虑它们的唯一性。 如果你想要在使用 json_build_object 的同时确保聚合的数组中的元素是唯一的...
r.locktype is not distinct from w.locktype and r.database is not distinct from w.database and r.relation is not distinct from w.relation and r.page is not distinct from w.page and r.tuple is not distinct from w.tuple and r.virtualxid is not distinct from w.virtualxid and r.trans...
以上示例中,我们使用了to_char函数将日期格式化为YYYY-MM-DD格式,使用to_json函数将查询结果转换为JSON格式,使用array_agg函数将多行结果聚合为一个数组,使用AS关键字给查询结果的列指定别名,使用DISTINCT关键字去重查询结果,使用ORDER BY关键字对查询结果进行排序。 请注意,以上示例中的"your_username"、"your_host"...
6. 数组去重 array(SELECT DISTINCT UNNEST regexp_split_to_array('1|2','\|')::int[] ) 7. 判断元素是否在数组中 SELECT 0 = ANY ('{1,2}'::int[]), SELECT 0 = ANY (lanes); 8. 分页大数据量的查询: SELECT id FROM (SELECT id, row_number() over(ORDER BY id) AS rownum FROM wa...
*aggcontext; int jumpdistinct; } agg_presorted_distinctcheck; /* for EEOP_AGG_PLAIN_TRANS_[INIT_][STRICT_]{BYVAL,BYREF} */ /* for EEOP_AGG_ORDERED_TRANS_{DATUM,TUPLE} */ struct { AggStatePerTrans pertrans; ExprContext *aggcontext; int setno; int transno; int setoff; } agg_trans...
begin-- 1. retrieve list of column names.dynsql1='select string_agg(distinct ''_''||'||colc||'||'' '||celldatatype||''','','' order by ''_''||'||colc||'||'' '||celldatatype||''') from '||tablename||';';executedynsql1intocolumnlist;-- 2. set up the crosstab ...
By combining array_to_string with array_agg, you can duplicate the behavior of string_agg. MySQL group_concat select salesperson, group_concat(customer order by contract_size desc separator ',') from customers group by 1 MySQL supports an optional distinct operator in group_concat: ...
select indrelid::regclass as tablename,array_agg(indexrelid::regclass) as indexes from pg_index group by indrelid,indkey having count(*) >1; 1. 检查长期未使用的索引。 mydb=# select relname,indexrelname,idx_scan from pg_catalog.pg_stat_user_indexes; 1. 检查无效的索引。 mydb=# select...
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:distinct (auto applies :array_agg & :to_jsonb) order_by [Symbol or Hash]: Applies an ordering operation (similar to ActiveRecord #order) Note: this option will be ignored if you need to order a DISTINCT Aggregated Array. physical_cat = Category.create!(name: "Physical") products = ...