obsidian-sync/work常用/数据库/PG 常用SQL.md

• 批量like

  like any (array['%.jpg','%.jpeg'])
  

• 创建序列

  create SEQUENCE id_seq
  START WITH 1
  INCREMENT BY 1
  NO MINVALUE
  NO MAXVALUE
  CACHE 1;
  
  alter table kx_hospital ALTER COLUMN id set DEFAULT nextval('_id_seq')
  

• 获取当前时间绝对秒

  select floor(extract(epoch from now()))
  

• 雪花ID函数

  create SEQUENCE table_id_seq
  START WITH 1
  INCREMENT BY 1
  NO MINVALUE
  NO MAXVALUE
  CACHE 1;
  
  CREATE OR REPLACE FUNCTION "public"."snow_next_id"(OUT "result" int8)
    RETURNS "pg_catalog"."int8" AS $BODY$
  DECLARE
     our_epoch bigint := 1314220021721;
     seq_id bigint;
     now_millis bigint;
     shard_id int := 5;
  BEGIN
     seq_id := nextval('table_id_seq') % 1024;
     SELECT FLOOR(EXTRACT(EPOCH FROM clock_timestamp()) * 1000) INTO now_millis;
     result := (now_millis - our_epoch) << 23;
     result := result | (shard_id << 10);
     result := result | (seq_id);
  END;
  $BODY$
    LANGUAGE plpgsql VOLATILE
    COST 100
  

• count统计过滤及去重

  count(distinct(speaker_id||speak_time||content)) FILTER (where t.mark='text')   ----- 使用distinct 去重 filter用于过滤
  

• PG 操作schema

  drop SCHEMA "public" CASCADE --强制删除，包含模式下所有对象（表、函数等）
  create SCHEMA "public" --创建
  alter schema name RENAME TO new_name -- 修改模式名称
  alter schema name OWNER TO new_owner -- 修改拥有者
  

• 获取单位时间间隔时间

  -- 获取6个月前时间
  select to_char((select now() - interval '6 month'),'yyyy-MM-dd hh24:mi:ss')
  

• 窗口函数分组统计(根据collect_code分组，并以collect_time 倒序)

  select collect_value,row_number() over(PARTITION by collect_code ORDER BY collect_time desc) from nc_data_collect_value_test
  

• lead函数获取上一条记录，并计算增量

  select create_date,node_value as total,next_day_total,next_day_total::int8-node_value::int8 as increment from (
  with a as (SELECT create_date, node_value FROM nc_data_node_value_detail WHERE node_code = '' ORDER BY create_date DESC )
  select create_date,node_value,lead(node_value,1) over (ORDER BY create_date) next_day_total FROM a ORDER BY create_date desc) tt
  

• lag函数获取下一条记录

  select create_date,node_value as total,next_day_total,abs(next_day_total::int8-node_value::int8) as increment from (
  with a as (SELECT create_date, node_value FROM nc_data_node_value_detail WHERE node_code = '' ORDER BY create_date DESC )
  select create_date,node_value,lag(node_value,1) over (ORDER BY create_date) next_day_total FROM a ORDER BY create_date desc) tt
  

• 序列生成

# 时间序列
# 例：生成从2021年到2023年
select to_char(generate_series(to_date('2021','yyyy'),to_date('2023','yyyy'),'1 years'),'yyyy')
# 生成今天24小时
select to_char(generate_series(to_timestamp(current_date || ' 00:00:00', 'yyyy-MM-dd HH24:mi:ss'),  
                       to_timestamp(current_date || ' 23:59:59', 'yyyy-MM-dd HH24:mi:ss'), '1 hour'),'yyyy-MM-dd HH24:mi:ss')

• 获取本月第1天和最后一天

select date_trunc('month',current_date),date_trunc('month',current_date)+interval '1 month - 1 day';