Tag Archives: CBO

Query Transformation playing with syntactically wrong SQL.

In Oracle whenever any SQL didn’t adhere syntax defined, it is bound to give some error. Any SQL is processed after syntax check is validated. In current blog will try to walk you through some SQL, that seems incorrect but … Continue reading

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Oracle 12c TOP N Pagination performance considerations.

In my post on TOP N and Pagination in Oracle 12c highlighted features introduce. In current post will try to compare performance and cardinality estimations for a scenario between INLINE ORDER BY + OUTER ROWNUM and TOP N IN 12C. … Continue reading

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Posted in Oracle 12c New Features, Oracle Internal | Tagged , , , , , | 1 Comment

SQL worked fine on pre 12c but failed with “ORA-01843: not a valid month” after upgrade.

Recently on OTN, OP posted below scenario. When he ran below SQL, it failed with “ORA-01843” in oracle 12c version. select FISCAL_SYSTEM_PERIOD_CAL_YR_EQ, calendrical_equivalent from fiscal_system_periods where calendrical_equivalent > 0 and to_date(FISCAL_SYSTEM_PERIOD_CAL_YR_EQ || ‘, ‘ || 2014,’Month, YYYY’) >= to_date(‘November, 2014’,’Month, … Continue reading

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