The SQL explain facility provides detailed information about the access plan that the query optimizer chooses for an SQL statement.
SQL解释工具提供查询优化器为 SQL语句所选择的访问计划的有关详细信息。
Db2exfmt requires that an SQL statement has been previously explained into these tables, and formats the contents of the information in the explain tables.
db 2 exfmt需要已经将一条sql语句解释到这些表中，并设置explain表中信息内容的格式。
This would result in the maximum value for MATCHCOLS when doing an EXPLAIN on the SQL statement.
这样一来，当对sql语句进行EXPLAIN时，就可以产生最大的matchcols值。
This would result in the maximum value for MATCHCOLS when doing an EXPLAIN on the SQL statement.
这样一来，当对sql语句进行EXPLAIN时，就可以产生最大的matchcols值。
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