是否有SQL语句可以返回表中列的类型?


当前回答

对于Apache Derby,如下面的答案所示:

select columndatatype from sys.syscolumns
  where referenceid = (
    select tableid from sys.systables
    where tablename = 'YOUR_TABEL_NAME'
    and columnname= 'YOUR_COLUMN_NAME')

其他回答

在oracle SQL中,你可以这样做:

SELECT
    DATA_TYPE
FROM
    all_tab_columns 
WHERE
    table_name = 'TABLE NAME' -- in uppercase
AND column_name = 'COLUMN NAME' -- in uppercase
USE [YourDatabaseName]
GO

SELECT column_name 'Column Name',
data_type 'Data Type'
FROM information_schema.columns
WHERE table_name = 'YourTableName'
GO

这将返回值Column Name,显示列的名称,以及这些列的数据类型(int, varchars等)。

由于有些人要求数据类型的精度,我想分享我为此目的而创建的脚本。

SELECT TABLE_NAME As 'TableName'
       COLUMN_NAME As 'ColumnName'
       CONCAT(DATA_TYPE, '(', COALESCE(CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, DATETIME_PRECISION, ''), IIF(NUMERIC_SCALE <> 0, CONCAT(', ', NUMERIC_SCALE), ''), ')', IIF(IS_NULLABLE = 'YES', ', null', ', not null')) As 'ColumnType'
FROM INFORMATION_SCHEMA.COLUMNS
WHERE -- ...
ORDER BY 'TableName', 'ColumnName'

这并不完美,但在大多数情况下都有效。

使用sql server

要检索实际声明的数据类型,例如在动态SQL To ALTER COLUMNs中使用,可以使用这样的方法:

SELECT
    TABLE_NAME, 
    COLUMN_NAME,
    DATA_TYPE
        + CASE WHEN DATA_TYPE IN ('char','nchar','varchar','nvarchar','binary','varbinary')
                    AND CHARACTER_MAXIMUM_LENGTH > 0 THEN
                 COALESCE('('+CONVERT(varchar,CHARACTER_MAXIMUM_LENGTH)+')','')
            ELSE '' END
        + CASE WHEN DATA_TYPE IN ('decimal','numeric') THEN
                COALESCE('('+CONVERT(varchar,NUMERIC_PRECISION)+','+CONVERT(varchar,NUMERIC_SCALE)+')','')
            ELSE '' END
        AS Declaration_Type,
    CASE WHEN IS_NULLABLE='NO' THEN 'NOT ' ELSE '' END + 'NULL' AS Nullable
FROM INFORMATION_SCHEMA.COLUMNS
ORDER BY 1,2

在我的情况下,我需要获得动态SQL的数据类型(Shudder!)无论如何,这里是一个函数,我创建返回完整的数据类型。例如,它不会返回'decimal',而是返回decimal (18,4): dbo。GetLiteralDataType