利用DB字典表查询表格字段定义

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-- 1、SQL Server表结构查询SQL
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    SELECT
        SO.name 表名,
        SC.name 表列名,
        ST.name 类型,
        SC.length 长度,
        case when exists(SELECT 1 FROMsysobjects where xtype='PK' and name in (SELECT name FROM sysindexes WHEREindid in(SELECT indid FROM sysindexkeys WHERE id = SC.id AND colid=SC.colid)))then '√' else '' end 主键,
        case when SC.isnullable=1 then'√'else '' end 允许为空,
        SC.colid 索引,
        SC.colorder 字段序号
    FROM
        sysobjects   SO, -- 对象表
        syscolumns   SC, -- 列名表
        systypes    ST  -- 数据类型表
    WHERE         
      SO.id = SC.id  
      AND   SO.xtype = 'U'   -- 类型U表示表，V表示视图
      AND   SO.status >=0    -- 非系统的临时表
      AND   SC.xtype = ST.xusertype
      AND   SO.name like 'BMP%'
    ORDER BY
        SO.name,SC.name         -- 按表名、列名排序

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-- 2. 如果从 ms sql 数据库中用一个复杂的sql语句，提取一个表的所有字段名称、类型、约束？
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--表结构
SELECT
        表名=case when a.colorder=1 thend.name else '' end,
        字段序号=a.colorder,
        字段名=a.name,
        标识=case when COLUMNPROPERTY(a.id,a.name,'IsIdentity')=1 then '√'else '' end,
        主键=case when exists(SELECT 1 FROMsysobjects where xtype='PK' and name in (
               SELECT name FROM sysindexes WHERE indid in(
                       SELECT indid FROM sysindexkeys WHERE id = a.id AND colid=a.colid
               ))) then '√' else '' end,
        类型=b.name,
        占用字节数=a.length,
        长度=COLUMNPROPERTY(a.id,a.name,'PRECISION'),
        小数位数=isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0),
        允许空=case when a.isnullable=1 then'√'else '' end,
        默认值=isnull(e.text,''),
        字段说明=isnull(g.[value],'')
FROM syscolumns a
        left join systypes b ona.xtype=b.xusertype
        inner join sysobjects d ona.id=d.id  and d.xtype='U' and  d.name<>'dtproperties'
        left join syscomments e ona.cdefault=e.id
        left join sysproperties g ona.id=g.id and a.colid=g.smallid 
--where d.name='要查询的表'    --如果只查询指定表,加上此条件
order by a.id,a.colorder

--表的外键约束
SELECT 表对象ID=b.fkeyid
        ,表名称=object_name(b.fkeyid)
        ,引用的列ID=b.fkey
        ,引用的列名=(SELECT name FROM syscolumnsWHERE colid=b.fkey AND id=b.fkeyid)
        ,引用的表对象ID=b.rkeyid
        ,引用的表名=object_name(b.rkeyid)
        ,已引用的列ID=b.rkey
        ,已引用的列名=(SELECT name FROMsyscolumns WHERE colid=b.rkey AND id=b.rkeyid)
FROM sysobjects a
        join sysforeignkeys b ona.id=b.constid
        join sysobjects c on a.parent_obj=c.id
where a.xtype='f' AND c.xtype='U'

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-- 3、PostgreSQL表结构查询SQL
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select
    a.table_name,
    a.column_name,
    a.is_nullable,
    a.udt_name,
    a.character_maximum_length,
    b.constraint_name,
    c.constraint_type as pk_type,
    d.indexrelname as index_name
from
    information_schema.columns a
    LEFT JOIN
        information_schema.KEY_COLUMN_USAGEb
        ON a.TABLE_NAME = b.table_name anda.column_name = b.column_name
    LEFT JOIN
        information_schema.TABLE_CONSTRAINTSc
        ON b.table_name = c.table_name andb.constraint_name =c.constraint_name
    LEFT JOIN
        pg_stat_user_indexes d
        ON c.TABLE_NAME = d.relname
where
    a.table_name in ( select TABLE_NAME frominformation_schema.tables where table_schema = 'public' and table_type= 'BASETABLE' and is_insertable_into = 'YES')
order by
    a.TABLE_NAME,a.COLUMN_NAME