是否有SQL语句可以返回表中列的类型?


当前回答

对于IBM DB2:

SELECT TYPENAME FROM SYSCAT.COLUMNS WHERE TABSCHEMA='your_schema_name' AND TABNAME='your_table_name' AND COLNAME='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

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')

对于IBM DB2:

SELECT TYPENAME FROM SYSCAT.COLUMNS WHERE TABSCHEMA='your_schema_name' AND TABNAME='your_table_name' AND COLNAME='your_column_name'

在TSQL中最简单的方法是:

SELECT COLUMN_NAME, DATA_TYPE 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = 'yourTableName'

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