Oracle – Facts About Primary Key vs. Unique Key You May Not Have Known

In this post we talk about Oracle specifically although some concepts apply to other databases. At a high level - PK's vs UK's Ask someone who has been doing database work about Primary Keys (PK) and Unique Keys (UK) and the differences between the two, they will tell you everything they know. Some even go into … Continue reading Oracle – Facts About Primary Key vs. Unique Key You May Not Have Known

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Oracle – Parallel To PGA (P2P) & Serial To SGA (S2S) – Caching Differences And When Parallelism Is Not The Panacea For Performance!

If you are running into memory issues such as below, there could be several causes but one of the causes is excessive parallelism and exhaustion of PGA memory. “ORA-01034: ORACLE not available / ORA-27102: out of memory / Linux-x86_64 Error: 12: Cannot allocate” Please read on to find out how to resolve this. There are … Continue reading Oracle – Parallel To PGA (P2P) & Serial To SGA (S2S) – Caching Differences And When Parallelism Is Not The Panacea For Performance!

Oracle – Explain Plan Basics & Brief History

Whenever a SQL statement is submitted to the database server (be it Oracle or SQL Server), the server generates an execution plan which it uses to get the data in a well-defined order. The engine that does this work is called the “optimizer”. History of optimizers: RBO – Rule based optimizer Back in the day, … Continue reading Oracle – Explain Plan Basics & Brief History

Oracle – LAG & LEAD – Usage Examples + Interesting Use-case

LAG and LEAD are a couple of analytic functions that come in handy in some interesting situations. I am not really sure why I wrote this post but at least it gives you a a few queries to play with LEAD and LAG. I am not completely happy with how this post turned out. Nothing … Continue reading Oracle – LAG & LEAD – Usage Examples + Interesting Use-case