SELECTAGEFROMCOMPANYWHEREEXISTS(SELECTAGEFROMCOMPANYWHERESALARY>65000); 以下的 SELECT 语句同样使用了 SQL 的子查询,子查询语句中读取SALARY(薪资)字段大于 65000 的AGE(年龄)字段数据,然后用>运算符查询大于该AGE(年龄)字段数据: SELECT*FROMCOMPANYWHEREAGE>(SELECTAGEFROMCOMPANYWHERESALARY>65000); SELECT 语句中...
postgres=# INSERT INTO demotable SELECT random() * 1000, generate_series(1, 1000000); INSERT 0 1000000 postgres=# analyze; ANALYZE Sequential Scan:顾名思义,顺序扫描就是顺序扫描对应表所有页的item指针。如果一个表有100页,每页有1000条记录,顺序扫描就会获取100*1000条记录并检查是满足可见性规则以及过...
select * from sort_random order by id; QUERY PLAN --- Sort (cost=211863.84..214363.84 rows=1000000 width=77) (actual time=3729.063..4418.530 rows=1000000 loops=1) Output: id, info, tm Sort Key: sort_random.id Sort Method: external merge Disk: 88120kB Buffers: shared hit=13334, temp...
(8 rows)# Seq Scan 顺序扫描mydb=# set max_parallel_workers_per_gather = 0;mydb=# explain analyze select * from testtable1 where tname='myname_10';QUERY PLAN --- Seq Scan on testtable1 (cost=0.00..94336.12 rows=1 width=18) (actual time=0.365..1828.760 rows=1 loops=1) Filter:...
INSERT INTO COMPANY1 (SELECT * FROM moved_rows 1. 2. 3. 4. 5. 6. 7. 11. HAVING 筛选分组后的各组数据 下面是 HAVING 子句在 SELECT 查询中的位置: SELECT FROM WHERE GROUP BY HAVING ORDER BY 1. 2. 3. 4. 5. 6. HAVING 子句必须放置于 GROUP BY 子句后面,ORDER BY 子句前面,下面是 ...
postgres=# insert into t1 select generate_series(11,1000), md5(random()::varchar);INSERT0990 1)查看meta块--bt_metap postgres=# select * from bt_metap('t1_pkey');-[RECORD1]---+---magic|340322version|4root|3level|1fastroot|3fastlevel|1last_cleanup_num_delpages|0last_cleanup_num...
Index Scan using idx_log_userid on log (cost=0.42..8.44 rows=1 width=16) Index Cond: (user_id = 81924442) (2 rows) 分区表log_par,根据user_id检索: explain select * from log_par where user_id = 81924442; postgres=# explain select * from log_par where user_id = 81924442; ...
PostgreSQL是一种开源的关系型数据库管理系统,它支持广泛的功能和扩展性。在PostgreSQL中,RIGHT()函数用于从字符串的右侧提取指定长度的字符。 然而,根据问题描述,可能存在RIG...
geqo_seed GEQO: seed for random path selection. geqo:种子随机路径选择。 geqo_selection_bias GEQO: selective pressure within the population. geqo:在人口压力。 geqo_threshold Sets the threshold of FROM items beyond which GEQO is used. 设置阈值的物品之外,geqo使用。 gin_fuzzy_search_limit Sets the...
(id INTEGER, fname TEXT, sname TEXT, lname TEXT, age INTEGER); postgres...postgres=# CREATE TABLE person(id INTEGER, name TEXT, type TEXT, divorced bool); postgres=# SELECT *...--- 1 | Alice | WOMAN | f 3 | Davis | KID | 2 | Bob | MAN | t (3 rows) NULL 的另一种用法...