关于oracle的序列调用问题

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　　在调用序列的CURRVAL 和NEXTVAL方法时，在一下SQL结构禁止使用
　　

• 　　A subquery in a DELETE, SELECT, or UPDATE statement
  
• 　　A query of a view or of a materialized view
  
• 　　A SELECT statement with the DISTINCT operator
  
• 　　A SELECT statement with a GROUP BY clause or ORDER BY clause
  
• 　　A SELECT statement that is combined with another SELECT statement with the UNION, INTERSECT, or MINUS set operator
  
• 　　The WHERE clause of a SELECT statement
  
• 　　The DEFAULT value of a column in a CREATE TABLE or ALTER TABLE statement
  
• 　　The condition of a CHECK constraint