SQL Server2005如何查询一个字段的最大长度

[proghua]

如有一个字段是类型char(30)，如何得到30

[快溜]

你自己定义的长度，你忘记了？

[proghua]

[Quote=引用 1 楼 ssp2009 的回复:]

你自己定义的长度，你忘记了？
[/Quote]
不是忘记了，是想在程序中动态获得

[Rotel-刘志东]

char(30) 30自己定义的长度。

[proghua]

我以前用Oracle的时候，Oralce有张视图user_tab_columns可以查到，sqlserver我不熟

[--小F--]

--sql server 2005
-- 1. 表结构信息查询 
-- ========================================================================
-- 表结构信息查询
-- 邹建 2005.08(引用请保留此信息)
-- ========================================================================
SELECT 
    TableName=CASE WHEN C.column_id=1 THEN O.name ELSE N'' END,
    TableDesc=ISNULL(CASE WHEN C.column_id=1 THEN PTB.[value] END,N''),
    Column_id=C.column_id,
    ColumnName=C.name,
    PrimaryKey=ISNULL(IDX.PrimaryKey,N''),
    [IDENTITY]=CASE WHEN C.is_identity=1 THEN N'√'ELSE N'' END,
    Computed=CASE WHEN C.is_computed=1 THEN N'√'ELSE N'' END,
    Type=T.name,
    Length=C.max_length,
    Precision=C.precision,
    Scale=C.scale,
    NullAble=CASE WHEN C.is_nullable=1 THEN N'√'ELSE N'' END,
    [Default]=ISNULL(D.definition,N''),
    ColumnDesc=ISNULL(PFD.[value],N''),
    IndexName=ISNULL(IDX.IndexName,N''),
    IndexSort=ISNULL(IDX.Sort,N''),
    Create_Date=O.Create_Date,
    Modify_Date=O.Modify_date
FROM sys.columns C
    INNER JOIN sys.objects O
        ON C.[object_id]=O.[object_id]
            AND O.type='U'
            AND O.is_ms_shipped=0
    INNER JOIN sys.types T
        ON C.user_type_id=T.user_type_id
    LEFT JOIN sys.default_constraints D
        ON C.[object_id]=D.parent_object_id
            AND C.column_id=D.parent_column_id
            AND C.default_object_id=D.[object_id]
    LEFT JOIN sys.extended_properties PFD
        ON PFD.class=1 
            AND C.[object_id]=PFD.major_id 
            AND C.column_id=PFD.minor_id
--             AND PFD.name='Caption'  -- 字段说明对应的描述名称(一个字段可以添加多个不同name的描述)
    LEFT JOIN sys.extended_properties PTB
        ON PTB.class=1 
            AND PTB.minor_id=0 
            AND C.[object_id]=PTB.major_id
--             AND PFD.name='Caption'  -- 表说明对应的描述名称(一个表可以添加多个不同name的描述) 
    LEFT JOIN                       -- 索引及主键信息
    (
        SELECT 
            IDXC.[object_id],
            IDXC.column_id,
            Sort=CASE INDEXKEY_PROPERTY(IDXC.[object_id],IDXC.index_id,IDXC.index_column_id,'IsDescending')
                WHEN 1 THEN 'DESC' WHEN 0 THEN 'ASC' ELSE '' END,
            PrimaryKey=CASE WHEN IDX.is_primary_key=1 THEN N'√'ELSE N'' END,
            IndexName=IDX.Name
        FROM sys.indexes IDX
        INNER JOIN sys.index_columns IDXC
            ON IDX.[object_id]=IDXC.[object_id]
                AND IDX.index_id=IDXC.index_id
        LEFT JOIN sys.key_constraints KC
            ON IDX.[object_id]=KC.[parent_object_id]
                AND IDX.index_id=KC.unique_index_id
        INNER JOIN  -- 对于一个列包含多个索引的情况,只显示第1个索引信息
        (
            SELECT [object_id], Column_id, index_id=MIN(index_id)
            FROM sys.index_columns
            GROUP BY [object_id], Column_id
        ) IDXCUQ
            ON IDXC.[object_id]=IDXCUQ.[object_id]
                AND IDXC.Column_id=IDXCUQ.Column_id
                AND IDXC.index_id=IDXCUQ.index_id
    ) IDX
        ON C.[object_id]=IDX.[object_id]
            AND C.column_id=IDX.column_id 
-- WHERE O.name=N'要查询的表'       -- 如果只查询指定表,加上此条件
ORDER BY O.name,C.column_id 

-- 2. 索引及主键信息 
-- ========================================================================
-- 索引及主键信息
-- 邹建 2005.08(引用请保留此信息)
-- ========================================================================
SELECT 
    TableId=O.[object_id],
    TableName=O.Name,
    IndexId=ISNULL(KC.[object_id],IDX.index_id),
    IndexName=IDX.Name,
    IndexType=ISNULL(KC.type_desc,'Index'),
    Index_Column_id=IDXC.index_column_id,
    ColumnID=C.Column_id,
    ColumnName=C.Name,
    Sort=CASE INDEXKEY_PROPERTY(IDXC.[object_id],IDXC.index_id,IDXC.index_column_id,'IsDescending')
        WHEN 1 THEN 'DESC' WHEN 0 THEN 'ASC' ELSE '' END,
    PrimaryKey=CASE WHEN IDX.is_primary_key=1 THEN N'√'ELSE N'' END,
    [UQIQUE]=CASE WHEN IDX.is_unique=1 THEN N'√'ELSE N'' END,
    Ignore_dup_key=CASE WHEN IDX.ignore_dup_key=1 THEN N'√'ELSE N'' END,
    Disabled=CASE WHEN IDX.is_disabled=1 THEN N'√'ELSE N'' END,
    Fill_factor=IDX.fill_factor,
    Padded=CASE WHEN IDX.is_padded=1 THEN N'√'ELSE N'' END
FROM sys.indexes IDX
    INNER JOIN sys.index_columns IDXC
        ON IDX.[object_id]=IDXC.[object_id]
            AND IDX.index_id=IDXC.index_id
    LEFT JOIN sys.key_constraints KC
        ON IDX.[object_id]=KC.[parent_object_id]
            AND IDX.index_id=KC.unique_index_id
    INNER JOIN sys.objects O
        ON O.[object_id]=IDX.[object_id]
    INNER JOIN sys.columns C
        ON O.[object_id]=C.[object_id]
            AND O.type='U'
            AND O.is_ms_shipped=0
            AND IDXC.Column_id=C.Column_id
--    INNER JOIN  -- 对于一个列包含多个索引的情况,只显示第1个索引信息
--    (
--        SELECT [object_id], Column_id, index_id=MIN(index_id)
--        FROM sys.index_columns
--        GROUP BY [object_id], Column_id
--    ) IDXCUQ
--        ON IDXC.[object_id]=IDXCUQ.[object_id]
--            AND IDXC.Column_id=IDXCUQ.Column_id

[gw6328]

select * from sys.all_columns -- sql2008这里面有个max_length

[快溜]

select name,
(select name from systypes where xtype=c.xtype)as type,length
 from syscolumns c 
where id=(select id from sysobjects where xtype='u' and name='busCabinet')

[Shawn]

CREATE TABLE TB
(
	a CHAR(30),
	b VARCHAR(10),
	c INT,
	d DECIMAL,
	e VARCHAR(MAX)
)
INSERT tb
SELECT 'a', 'b', 1, 1.00, 'e'
--SQL:
SELECT 
	LEN(a),
	LEN(b),
	LEN(c),
	LEN(d),
	LEN(e)
FROM dbo.tb
/*
1	1	1	1	1
*/
SELECT 
	DATALENGTH(a),
	DATALENGTH(b),
	DATALENGTH(c),
	DATALENGTH(d),
	DATALENGTH(e)
FROM dbo.tb
/*
30	1	4	5	1
*/
--最大长度
SELECT [name], max_length FROM sys.columns WHERE object_id = 
(SELECT TOP(1) object_id FROM sys.tables WHERE [name] = 'tb')
/*
a	30
b	10
c	4
d	9
e	-1
*/

[王向飞]

select OBJECT_NAME(id),name,length from syscolumns

[proghua]

OK, sys.columns和sys.tables连接一下

[renwenli07461]

根据表名查出

SELECT sys.all_columns.name as 字段名,MAX_LENGTH as 字段长度 FROM sys.all_columns
  INNER JOIN sysobjects ON sysobjects.ID=sys.all_columns.object_id
WHERE sysobjects.xtype='U' AND sysobjects.name='表名'

[miaoyunning]

SELECT top 1 [name],length FROM syscolumns WHERE id in (SELECT TOP 1 id FROM sysobjects WHERE [name] = 'tabname') order by length desc