Oracle数据库一向给我们功能强大的印象,殊不知Oracle内部也是有各种限制的. 今天我们就说说数据类型的限制,也就是数据类型的取值范围: 数据类型 限制 注释 BFILE Maximum size: 4 GB 文件最大4G The maximum number of BFILEs is limited by the value of the SESSION_MAX_OPEN_FILES initialization parameter, which is itself limited by the maximum number of open files the operating system will allow. BFILE最大可打开数量由参数SESSION_MAX_OPEN_FILES 决定 而SESSION_MAX_OPEN_FILES参数的最大值由操作系统允许打开的最大文件数量所决定 Maximum size of a file name: 255 characters 文件名最长255字符 Maximum size of a directory name: 30 characters 目录名最长30字符 Maximum number of open BFILEs: see Comments 最大可以同时打开的熟练参见注释 BLOB Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB) 最大大小为 (4 GB - 1) * DB_BLOCK_SIZE. 根据块大小不同范围为8TB到128TB. The number of LOB columns per table is limited only by the maximum number of columns per table 一个表中可包含的LOB列的多少由表中最大列数量决定 CHAR Maximum size: 2000 bytes CHAR类型最长为2000字节 None CHAR VARYING Maximum size: 4000 bytes CHAR 变量最长为4000 字节 None CLOB Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB) The number of LOB columns per table is limited only by the maximum number of columns per table The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref ). Literals (characters or numbers in SQL or PL/SQL) Maximum size: 4000 characters 字面值:最长4000个字节 None LONG Maximum size: 2 GB - 1 最长大小为 2GB-1 Only one LONG column is allowed per table. NCHAR Maximum size: 2000 bytes 最长大小为2000字节 None NCHAR VARYING Maximum size: 4000 bytes, or 32767 bytes if the MAX_STRING_SIZE initialization parameter is set to EXTENDED NCHAR 变量为4000 如果设置MAX_STRING_SIZE为EXTENDED,最大可支持32767个字节 None See Also: "MAX_STRING_SIZE" initialization parameter for additional details NCLOB Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB) 最大大小为 (4 GB - 1) * DB_BLOCK_SIZE. 根据块大小不同范围为8TB到128TB. The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref ). 一个表中可包含的LOB列的多少由表中最大列数量决定 NUMBER 最大值999...(38 9's) x10125 Can be represented to full 38-digit precision (the mantissa) 最小值-999...(38 9's) x10125 Can be represented to full 38-digit precision (the mantissa) Precision(精度) 38 significant digits None RAW Maximum size: 2000 bytes, or 32767 bytes if the MAX_STRING_SIZE initialization parameter is set to EXTENDED 最大大小为2000字节,如果设置MAX_STRING_SIZE参数为 EXTENDED则为32767 None See Also: "MAX_STRING_SIZE" initialization parameter for additional details VARCHAR Maximum size: 4000 bytes 最长为4000字节 None VARCHAR2 Maximum size: 4000 bytes, or 32767 bytes if the MAX_STRING_SIZE initialization parameter is set to EXTENDED 最大大小为4000字节,如果设置MAX_STRING_SIZE参数为 EXTENDED则为32767 None See Also: "MAX_STRING_SIZE" initialization parameter for additional details 原文：http://t.bosenrui.com/dba/a9ad307866880646d66762fb2a349682.html