SQL Server2005如何查询一个字段的最大长度

2011-03-16 04:24:34 950 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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如有一个字段是类型char(30)，如何得到30

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切换为时间正序

miaoyunning 2011-03-16

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

renwenli07461 2011-03-16

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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'

「已注销」 2011-03-16

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OK, sys.columns和sys.tables连接一下

王向飞 2011-03-16

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select OBJECT_NAME(id),name,length from syscolumns

Shawn 2011-03-16

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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

*/

快溜 2011-03-16

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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')

gw6328 2011-03-16

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

--小F-- 2011-03-16

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--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