SQL Comments
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Comments in SQL play a crucial role in clarifying code sections and preventing certain statements from execution. They come in three formats:
- Single-line comments: Brief explanations written on a single line using "--".
- Multi-line comments: Detailed comments spanning multiple lines enclosed within "/* */".
- In-line comments: Comments placed within SQL statements to clarify specific parts of the code.
Single Line Comments
Definition
The SQL allows you to make single-line comments by using the two dashes (--). The SQL server ignores the text that appears after the two dashes on a single line.
The query shown below illustrates how to create comments in SQL on a single line.
Syntax
Examples
- Description of Query Purpose:
- Temporary Disabling a Query:
- Debugging or Clarification:
Multi-Line Comments
Definition
The single-line comments in sql work only if the comment is of a single line. If you want to add a large comment that spans across multiple lines then you have to put a double dash on every single line. But there is another way and more efficient way to add multi-line comments in SQL.
You can add the multi-line comments in SQL that starts with the /* and ends with the */. The content or the description written inside these is ignored by the SQL server. The below-given query explains how you can add multi-line comments in SQL.
Syntax
Examples
- Description of Query Block:
- Temporary Disabling a Block of Code:
- Explanation of Complex Logic:
In-line Comments
Definition
The third type of comment is Inline comments in sql and which is an extension of the multi-line comment. Inline comments in SQL can be added between the SQL statements and are enclosed within /* and */. The below-given query explains how you can add inline comments in SQL.
Syntax
Examples
- Inline comment within a table name in a SELECT statement:
- Inline comment within a table name in a JOIN operation:
- Inline comment within a table name in a WHERE clause:
Conclusion
- Clarity and Documentation: Comments in SQL provide descriptive explanations, making SQL code easier to understand for developers and future maintainers.
- Prevention of Execution: By commenting out certain statements, developers can temporarily disable code segments without deleting them, aiding in debugging and testing processes.
- Code Structure and Organization: Multi-line comments in SQL allow for the grouping of related SQL statements, enhancing code structure and organization.
- Facilitation of Collaboration: Well-commented SQL code promotes collaboration among team members by conveying the purpose and logic behind queries and database operations.
- Enhanced Debugging: Comments in SQL serve as valuable aids during the debugging process, providing insights into the intended functionality of specific code sections.
- Efficient Query Development: In-line comments in SQL SQL statements offer real-time explanations of table joins, filtering criteria, and other query components, streamlining query development and optimization efforts.