oracle sql execution process

Oracle SQL is the most commonly used and most powerful database language in relational database management systems. When using Oracle SQL to perform data queries, operations, etc., you need to understand the execution process of Oracle SQL. This article will introduce the execution process of Oracle SQL so that readers can better understand and master the use of Oracle SQL.

The basic execution process of Oracle SQL

The execution process of Oracle SQL can be divided into the following steps:

1. Parsing the SQL statement: Oracle SQL first needs to issue a Parse the SQL statement to determine whether the syntax of the SQL statement is correct and whether the semantics are reasonable. If the SQL statement has no syntax errors, the SQL statement will be parsed semantically and an execution plan will be generated.
2. Generate execution plan: Generating execution plan is an important step in Oracle SQL, which determines how Oracle SQL performs query operations. An execution plan is a thorough execution plan that covers every step from start to finish, including establishing connections, locating data, performing operations, returning results, etc.
3. Execute SQL statements: After generating the execution plan, Oracle SQL will execute the SQL statements. Executing a SQL statement actually follows the steps in the execution plan. Oracle SQL will execute each step from establishing the connection to finally returning the results in sequence according to the order specified in the execution plan.
4. Return results: When Oracle SQL completes executing the SQL statement, it will return the execution results. The form of returned results includes query result set, number of modified records, error information, etc.

The execution flow chart of Oracle SQL is shown below:

Optimization execution process of Oracle SQL

In order to improve Oracle SQL execution efficiency and performance, Oracle SQL also has an optimization execution process, which includes the following steps:

1. Identify bottlenecks in the SQL execution plan: Oracle SQL will find in the execution plan that affect query efficiency Bottlenecks include cache misses, costly queries, different sequential execution plans, incorrect index selection, etc.
2. Optimize execution plan: After identifying the bottleneck, Oracle SQL will try to optimize the execution plan. The optimization process includes re-hitting the cache, rewriting query statements, changing array size, optimizing subqueries, etc.
3. Reconstruct the SQL statement: If the SQL statement cannot be optimized through simple optimization methods, Oracle SQL will reconstruct the SQL statement. Reconstructing SQL statements includes modifying query statements, adding indexes, redesigning table structures, etc.
4. Re-execute the SQL statement: After reconstructing the SQL statement, Oracle SQL will re-execute the SQL statement and return the execution results.

The flow chart of the optimization execution process of Oracle SQL is shown below:

Summary

This article introduces the optimization of Oracle SQL Basic execution process and optimized execution process. When using Oracle SQL for queries and operations, it is very important to understand the execution process of Oracle SQL, which can help readers better understand the use of Oracle SQL and optimize query efficiency and performance. In practical applications, the reasonable use of Oracle SQL optimization technology can help the system process data faster and improve the efficiency and availability of the database system.

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