UNNET operator有offset但是没有offset as的时候，如下面语句，解析器报错
SELECT * FROM UNNEST ([10,20,30]) as numbers WITH OFFSET;

Exception in thread "main" com.alibaba.druid.sql.parser.ParserException: ERROR. pos 57, line 1, column 57, token ;
at com.alibaba.druid.sql.parser.SQLExprParser.primary(SQLExprParser.java:1259)
at com.alibaba.druid.sql.dialect.bigquery.parser.BigQueryExprParser.primary(BigQueryExprParser.java:298)
at com.alibaba.druid.sql.parser.SQLExprParser.expr(SQLExprParser.java:110)
at com.alibaba.druid.sql.parser.SQLSelectParser.parseUnnestTableSource(SQLSelectParser.java:1404)
at com.alibaba.druid.sql.parser.SQLSelectParser.parseTableSource(SQLSelectParser.java:1321)
at com.alibaba.druid.sql.parser.SQLSelectParser.parseFrom(SQLSelectParser.java:1197)
at com.alibaba.druid.sql.parser.SQLSelectParser.query(SQLSelectParser.java:504)
at com.alibaba.druid.sql.parser.SQLSelectParser.select(SQLSelectParser.java:78)
at com.alibaba.druid.sql.parser.SQLStatementParser.parseSelect(SQLStatementParser.java:4872)
at com.alibaba.druid.sql.parser.SQLStatementParser.parseStatementList(SQLStatementParser.java:233)
at com.alibaba.druid.sql.parser.SQLStatementParser.parseStatementList(SQLStatementParser.java:108)