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Exp Parameter : STATISTICS

原创 IT综合 作者:tsinglee 时间:2007-09-20 17:27:23 0 删除 编辑

Specifies the type of database optimizer statistics to generate when the
exported data is imported. Options are ESTIMATE,COMPUTE, and NONE.
In some cases, Export will place the precalculated statistics in the export file
as well as the ANALYZE statements to regenerate the statistics.
However, the precalculated optimizer statistics will not be used at export time
if a table has columns with system-generated names.
The precalculated optimizer statistics are flagged as questionable at export
time if:
■ There are row errors while exporting
■ The client character set or NCHAR character set does not match the server
character set orNCHAR character set
■ A QUERY clause is specified
■ Only certain partitions or subpartitions are exported

2. ANALYZE语句可重新生成统计信息并替代预先计算好的统计信息
3. 如果表中有系统自动命名的字段 ,在导出时不会使用预先计算好的统计信息
4. 在以下情况下 , 预先计算好的统计信息会被标记为可疑的:
a. 客户端字符集与服务器端字符集不匹配
b. 有query条件
c. 部分分区或者几分区
d. 导出时错误
5. 默认值为 : ESTIMATE


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