例如,可以使用to_char函数将日期类型的数据格式化为特定的字符串格式,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等。 使用查询选项:在执行查询时,可以使用查询选项来指定输出格式。例如,可以使用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...
方法一:使用子查询和 DISTINCT 你可以先创建一个子查询来选择唯一的值,然后在外部查询中使用 array_agg 和json_build_object。 代码语言:txt 复制 SELECT json_build_object( 'unique_values', array_agg(DISTINCT value) ) FROM ( SELECT DISTINCT value FROM your_table ) sub; 在这个例子中,子查询首先选择...
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...
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...
(More details in the Citus 12.1 release notes.) \n PG16: JSON aggregate support: As of Citus 12.1, Citus now supports and parallelizes the new JSON_ARRAYAGG() and JSON_OBJECTAGG() aggregates. (Code example in the 12.1 release notes.)\n PG16: DEFAULT in COPY: B...
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 ...
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...
: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 = ...
" ORDER BY wiki_revision.id SEPARATOR ', '), " "dashboards_wikidocumentvisits.visits " "STRING_AGG(DISTINCT auth_user.username, ', ' ORDER BY auth_user.username), " "MAX(dashboards_wikidocumentvisits.visits) visits " "FROM wiki_document " "INNER JOIN wiki_revision ON " " wiki_docum...