postgresql 常用SQL语句小结

发布时间：2024-03-08 05:44:56 来源：互联网

1、查询链接数 SELECT sum(numbackends) FROM pg_stat_database; 2、查看死锁状态 select pid,usena

1、查询链接数

SELECT sum(numbackends) FROM pg_stat_database;

2、查看死锁状态

select pid,
       usename,
       pg_blocking_pids(pid) as blocked_by,
       query as blocked_query
from pg_stat_activity
where cardinality(pg_blocking_pids(pid)) > 0;

3、删除死锁进程

SELECT pg_cancel_backend(__pid__);
SELECT pg_terminate_backend(__pid__);

4、备份数据库

# sql文件
pg_dump dangerousdb > db.sql
# tar文件
pg_dump -U postgres -F c dangerousdb > dangerousdb.tar
# gz文件
pg_dump -U postgres dangerousdb | gzip > dangerousdb.gz

5、还原数据库

# 已经存在数据库
pg_restore -U postgres -Ft -d dbcooper < dbcooper.tar
# 创建新数据库
pg_restore -U postgres -Ft -C -d dbcooper < dbcooper.tar
#

6、插入数据

插入单条数据

INSERT INTO TABLE_1
(
column_1,
column_2,
column_3
)
values(
column_1,
column_2,
column_3
)

插入多条数据

INSERT INTO TABLE_1
(
column_1,
column_2,
column_3
)
values(
column_1,
column_2,
column_3
),(
column_1,
column_2,
column_3
)...

从一张表查询到的数据插入到另一张表

INSERT INTO TABLE_1
(
column_1,
column_2,
column_3
)
SELECT
column_1,
column_2,
column_3
FROM
TABLE_2
where TABLE_2条件;

7 、查询pg中单张表的大小（不包含索引）

select
    pg_size_pretty(pg_relation_size('schema.table_name'));

8、查询数据库中所有表的大小

select
    relname,
    pg_size_pretty(pg_relation_size(relid))
from
    pg_stat_user_tables
where
    schemaname = 'public'
order by
    pg_relation_size(relid) desc;

9、按顺序查看索引

select
    indexrelname,
    pg_size_pretty(pg_relation_size(relid))
from
    pg_stat_user_indexes
where
    schemaname = 'public'
order by
    pg_relation_size(relid) desc;

10 、查询数据库的大小

select
    pg_database.datname,
    pg_size_pretty (pg_database_size(pg_database.datname)) as size
from
    pg_database;

11、查询被锁定的表

select
    pg_class.relname as table,
    pg_database.datname as database,
    pid,
    mode,
    granted
from
    pg_locks,
    pg_class,
    pg_database
where
    pg_locks.relation = pg_class.oid
    and pg_locks.database = pg_database.oid;

12 、查询一个Schema下面的所有表的总大小（单位MB，包括索引和数据）

select
    schemaname ,
    round(sum(pg_total_relation_size(schemaname || '.' || tablename))/ 1024 / 1024) "Size_MB"
from
    pg_tables
where
    schemaname = '<schemaname>'
group by
    1;

13 、查询所有表的大小并排序（包含索引）

select
    table_schema || '.' || table_name as table_full_name,
    pg_size_pretty(pg_total_relation_size('"' || table_schema || '"."' || table_name || '"')) as size
from
    information_schema.tables
order by
    pg_total_relation_size('"' || table_schema || '"."' || table_name || '"') desc
limit 20;

14 、查询表大小按大小排序并分离data与index

select
    table_name,
    pg_size_pretty(table_size) as table_size,
    pg_size_pretty(indexes_size) as indexes_size,
    pg_size_pretty(total_size) as total_size
from
    (
    select
        table_name,
        pg_table_size(table_name) as table_size,
        pg_indexes_size(table_name) as indexes_size,
        pg_total_relation_size(table_name) as total_size
    from
        (
        select
            ('"' || table_schema || '"."' || table_name || '"') as table_name
        from
            information_schema.tables) as all_tables
    order by
        total_size desc) as pretty_sizes;

或者

select
    table_name,
    pg_size_pretty(table_size) as table_size,
    pg_size_pretty(indexes_size) as indexes_size,
    pg_size_pretty(total_size) as total_size
from
    (
    select
        table_name,
        pg_table_size(table_name) as table_size,
        pg_indexes_size(table_name) as indexes_size,
        pg_total_relation_size(table_name) as total_size
    from
        (
        select
            ('' || table_schema || '.' || table_name || '') as table_name
        from
            information_schema.tables) as all_tables
    order by
        total_size desc) as pretty_sizes;

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