达梦数据库sql笔记

文章目录

[1 日期时间函数](#1 日期时间函数)
- [1.1 now()](#1.1 now())
[2 权限相关](#2 权限相关)
[3 锁](#3 锁)
- [3.1 某张表上的某种锁是由哪个会话操作加上的](#3.1 某张表上的某种锁是由哪个会话操作加上的)
[4 表空间](#4 表空间)
[5 查看一个模式下的每一张表占据的硬盘空间的大小](#5 查看一个模式下的每一张表占据的硬盘空间的大小)

1 日期时间函数

1.1 now()

语法：NOW(n)

功能：返回系统的当前时间戳。等价于 GETDATE()。

参数：n：指定毫秒的精度。取值范围 0-6，默认为 6。

2 权限相关

为一个用户移除 PUBLIC 角色（默认可能隐含权限）

sql 复制代码

REVOKE PUBLIC FROM WY_RES_READ;

1、创建一个角色，并将一个模式下的所有的表的查询权限赋给创建好的角色，然后将角色赋给另外一个用户。

sql 复制代码

-- 创建只读角色
--CREATE ROLE WY_GQ_IIMS_READONLY;

-- 授权角色访问模式下的所有表
BEGIN
    FOR rec IN (
        SELECT TABLE_NAME 
		FROM ALL_TABLES 
		WHERE OWNER = 'WY_GQ_IIMS'
    ) 
    LOOP
        EXECUTE IMMEDIATE 
            'GRANT SELECT ON WY_GQ_IIMS.' || rec.TABLE_NAME || ' TO WY_GQ_IIMS_READONLY';
    END LOOP;
END;
/

-- 将角色授予用户
GRANT WY_GQ_IIMS_READONLY TO WY_RES_READ;

3 锁

3.1 某张表上的某种锁是由哪个会话操作加上的

sql 复制代码

select 
	a.*,b.NAME,c.SESS_ID,c.CLNT_IP,c.SQL_TEXT 
from 
	v$lock a
	left join sysobjects b on b.ID=a.TABLE_ID
	left join v$sessions c on a.TRX_ID=c.TRX_ID
where 
	b.NAME LIKE '%recent_a%'
	and c.CREATE_TIME > '2025-08-05';

4 表空间

sql 复制代码

SELECT 
  ID AS "表空间ID",
  NAME AS "表空间名称",
  CACHE AS "缓存策略",
  TYPE$ AS "类型（0=数据，1=临时，2=回滚）",
  STATUS$ AS "状态（0=联机，1=脱机）",
  TOTAL_SIZE*16/1024/1024 AS "总大小(GB)",
  USED_SIZE*16/1024/1024 AS "已使用大小(GB)"
FROM 
	V$TABLESPACE
order by USED_SIZE DESC;

select tablespace_name,file_name,status, bytes/1024/1024/1024 as "GB" from DBA_DATA_FILES order by "GB" DESC;

-- 查看页大小
SELECT SF_GET_PAGE_SIZE();

select 
	*
FROM 
	V$TABLESPACE;

select * from DBA_DATA_FILES;

5 查看一个模式下的每一张表占据的硬盘空间的大小

sql 复制代码

SELECT 
    t.owner AS "模式",
    t.table_name AS "表名",
    ROUND(COALESCE(s.seg_size, 0) / 1024 / 1024, 2) AS "表数据空间(MB)",
    ROUND(COALESCE(idx.idx_size, 0) / 1024 / 1024, 2) AS "索引空间(MB)",
    ROUND(COALESCE(s.seg_size + idx.idx_size, 0) / 1024 / 1024 / 1024, 2) AS "总占用空间(GB)"
FROM 
    dba_tables t
LEFT JOIN 
    (SELECT owner, segment_name, SUM(bytes) AS seg_size 
     FROM dba_segments 
     WHERE segment_type = 'TABLE' 
     GROUP BY owner, segment_name) s 
    ON t.owner = s.owner AND t.table_name = s.segment_name
LEFT JOIN 
    (SELECT i.owner, i.table_name, SUM(s.bytes) AS idx_size 
     FROM dba_indexes i 
     JOIN dba_segments s ON i.index_name = s.segment_name 
     WHERE s.segment_type = 'INDEX' 
     GROUP BY i.owner, i.table_name) idx 
    ON t.owner = idx.owner AND t.table_name = idx.table_name
WHERE 
    t.owner = 'SJZT_MD'  -- 替换为实际模式名
ORDER BY 
    "总占用空间(GB)" DESC;


select 
	sum("总占用空间(GB)")
from (
SELECT 
    t.owner AS "模式",
    t.table_name AS "表名",
    ROUND(COALESCE(s.seg_size, 0) / 1024 / 1024, 2) AS "表数据空间(MB)",
    ROUND(COALESCE(idx.idx_size, 0) / 1024 / 1024, 2) AS "索引空间(MB)",
    ROUND(COALESCE(s.seg_size + idx.idx_size, 0) / 1024 / 1024 / 1024, 2) AS "总占用空间(GB)"
FROM 
    dba_tables t
LEFT JOIN 
    (SELECT owner, segment_name, SUM(bytes) AS seg_size 
     FROM dba_segments 
     WHERE segment_type = 'TABLE' 
     GROUP BY owner, segment_name) s 
    ON t.owner = s.owner AND t.table_name = s.segment_name
LEFT JOIN 
    (SELECT i.owner, i.table_name, SUM(s.bytes) AS idx_size 
     FROM dba_indexes i 
     JOIN dba_segments s ON i.index_name = s.segment_name 
     WHERE s.segment_type = 'INDEX' 
     GROUP BY i.owner, i.table_name) idx 
    ON t.owner = idx.owner AND t.table_name = idx.table_name
WHERE 
    t.owner = 'SJZT_MD'  -- 替换为实际模式名
ORDER BY 
    "总占用空间(GB)" DESC
)