This category contains 13 posts

A Short Guide to Oracle SQL [X] – Other Database Objects [Index]

Indexes are optional database objects that (if used properly) can increase the performance of queries. When retrieve data from the table Oracle has two options to do, First reads every row in the table (Full Table scan) or use the index to find the relevant rows quickly. Full table scan in itself is a resource … Continue reading

A Short Guide to Oracle SQL [X] – Other Database Objects (Sequences & Synonyms)

This is last topic in this series. Till now we talked about a major database object “Table“. Apart from tables there are some other objects which is used more commonly and frequently. These are Indexes, Sequences, Synonyms and Views. An Index is an optional db object that provide faster access path to table data. Sequence … Continue reading

A Short Guide to Oracle SQL [IX] – User management

DCL Statements Data Control Language (DCL) used to control access to the database and the data reside in it. It enforce data security. DCL statements preserve the security of data within the database and ensure that no one but the authorised user is able to view or change data. GRANT statement is used to provide … Continue reading

A Short Guide to Oracle SQL [VIII] – Subqueries

Subqueries A subquery is a nested query – a query within a query. A subquery’s output are used to determine the results of the outer query (the query that contains the subquery). Subqueries can be used in SELECT, FROM, WHERE and HAVING clause. Subquery has the same form as SELECT statement except it is enclosed … Continue reading

A Short Guide to Oracle SQL [VII] – Aggregate Functions

Group function takes an entire column of data or set of data as its arguments and produces a single result that summarizes the set of data. The most commonly used Aggregate functions are COUNT, SUM, AVG, MAX, and MIN. Aggregate functions can appear in SELECT lists and in ORDER BY and HAVING clauses. Here we … Continue reading

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