SQL

 This chapter provides an overview of the Structured Query Language (SQL) and how Oracle Database processes SQL statements.

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This chapter includes the following topics:

• Introduction to SQL

• Overview of SQL Statements

• Overview of the Optimizer

• Overview of SQL Processing

Introduction to SQL

SQL (pronounced sequel) is the set-based, high-level declarative computer language with which all programs and users access data in an Oracle database.

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Although some Oracle tools and applications mask SQL use, all database tasks are performed using SQL. Any other data access method circumvents the security built into Oracle Database and potentially compromises data security and integrity.

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SQL provides an interface to a relational database such as Oracle Database. SQL unifies tasks such as the following in one consistent language:

• Creating, replacing, altering, and dropping objects

• Inserting, updating, and deleting table rows

• Querying data

• Controlling access to the database and its objects

• Guaranteeing database consistency and integrity

SQL can be used interactively, which means that statements are entered manually into a program. SQL statements can also be embedded within a program written in a different language such as C or Java.

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