# 如何查询数据库、表空间、表的大小？
- 查询数据库大小：
  ```
  gaussdb=#  SELECT datname, pg_database_size(datname), pg_database_size(datname)/1024/1024/1024 as "dataSize_GB" FROM pg_database;
         datname       | pg_database_size |    dataSize_GB    
  ---------------------+------------------+-------------------
   template1           |         79208460 | .0737686268985271
   template0           |         79208460 | .0737686268985271
   postgres            |       1398554636 |  1.30250550433993
   mysql_compatible_db |         79208460 | .0737686268985271
  (4 rows)
  ```
  
- 查询表空间大小：
  ```
  gaussdb=#  SELECT pg_size_pretty(pg_tablespace_size('pg_default'));
   pg_size_pretty 
  ----------------
   345 MB
  (1 row)
  ```
  

- 查询表大小：
  ```
  gaussdb=#  SELECT pg_size_pretty(pg_relation_size('table_name'));
  pg_size_pretty 
  ----------------
   0 bytes
  (1 row)
  ```