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| <!DOCTYPE html> | ||
| <html lang="en"> | ||
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| <head> | ||
| <meta charset="UTF-8"> | ||
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> | ||
| <script src="https://cdn.tailwindcss.com"></script> | ||
| <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css"> | ||
| <link rel="stylesheet" href="../css/tutorial.css"> | ||
| <link rel="stylesheet" href="../css/default.css"> | ||
| <title>Learn SQL | Filtering Data</title> | ||
| </head> | ||
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| <body> | ||
| <div class="sidenav"> | ||
| <div class="logo"> | ||
| <a href="../index.html" class="header">Learn SQL</a> | ||
| <p>With <a href="#">Me😊</a></p> | ||
| </div> | ||
| <div class="topics"> | ||
| <a href="database.html" class="topic">Database</a> | ||
| <a href="basic_sql_queries.html" class="topic">Basic SQL Queries</a> | ||
| <a href="#" class="topic ">Filtering Data</a> | ||
| <a href="working_with_functions.html" class="topic">Working with Functions</a> | ||
| <a href="joining_tables.html" class="topic">Joining Tables</a> | ||
| <a href="sub_queries.html" class="topic">Subqueries</a> | ||
| <a href="modifying_data.html" class="topic">Modifying Data</a> | ||
| <a href="advanced_queries.html" class="topic">Advanced Queries</a> | ||
| <a href="transactions_and_locking.html" class="topic ">Transactions and Locking</a> | ||
| <a href="indexing_and_optimization.html" class="topic active">Indexing and Optimization</a> | ||
| <a href="sql_best_practices.html" class="topic">SQL Best Practices</a> | ||
| </div> | ||
| <div class="social-icons"> | ||
| <!-- linkedin --> | ||
| <a href="https://www.linkedin.com/in/prayushadhikari/" class="social-link"> | ||
| <i class="bi bi-linkedin"></i> | ||
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| <a href="https://www.github.com/adhikareeprayush" class="social-link"> | ||
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| </a> | ||
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| </div> | ||
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| </div> | ||
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| <div class="content"> | ||
| <div class="subtopics"> | ||
| <div id="indexes_in_sql" class="id_topic"> | ||
| <div class="question"> | ||
| <h2>Indexes in SQL</h2> | ||
| <p>Indexes are used to retrieve data from the database more quickly than otherwise. The users cannot | ||
| see the indexes, they are just used to speed up searches/queries.</p> | ||
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| <h3>Types of Indexes</h3> | ||
| <p>There are three types of indexes:</p> | ||
| <ul> | ||
| <li>- Unique Index</li> | ||
| <li>- Clustered Index</li> | ||
| <li>- Non-Clustered Index</li> | ||
| </ul> | ||
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| <h3>Unique Index</h3> | ||
| <p>Unique Indexes are used not just for performance but for data integrity as well, as they do not | ||
| allow the field to have duplicate values if the column is unique indexed.</p> | ||
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| <h3>Clustered Index</h3> | ||
| <p>Clustered Indexes are the indexes that physically sort the data rows in the table on the basis of | ||
| their key values. There can be only one clustered index on a table.</p> | ||
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| <h3>Non-Clustered Index</h3> | ||
| <p>Non-Clustered Indexes are the indexes where the logical order of the index does not match the | ||
| physical stored order of the rows on disk. The leaf layer of a non-clustered index does not | ||
| consist | ||
| of the data pages. Instead, the leaf nodes contain index rows.</p> | ||
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| </div> | ||
| </div> | ||
|
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| <div id="query_optimization_techniques" class="id_topic"> | ||
| <div class="question"> | ||
| <h2>Query Optimization Techniques</h2> | ||
| <p>Query optimization is the process of selecting the most efficient way to execute a query. The | ||
| process of optimization is a complex one, as it involves making decisions based on the available | ||
| statistics and the query plan. The query optimizer is the component of the database management | ||
| system that performs this optimization.</p> | ||
|
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| <h3>Types of Query Optimization Techniques</h3> | ||
| <p>There are several query optimization techniques:</p> | ||
| <ul> | ||
| <li>- Join Elimination</li> | ||
| <li>- Indexing</li> | ||
| <li>- Query Rewriting</li> | ||
| <li>- Query Decomposition</li> | ||
| <li>- Query Compilation</li> | ||
| <li>- Query Execution</li> | ||
| </ul> | ||
|
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| <h3>Join Elimination</h3> | ||
| <p>Join elimination is the process of removing joins from a query that are not necessary for the | ||
| query to return the correct results. This can be done by using indexes or by rewriting the query | ||
| to eliminate the join.</p> | ||
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| <h3>Indexing</h3> | ||
| <p>Indexing is the process of creating indexes on the columns that are frequently used in queries. | ||
| This can speed up the query by allowing the database to quickly locate the rows that match the | ||
| query criteria.</p> | ||
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| <h3>Query Rewriting</h3> | ||
| <p>Query rewriting is the process of rewriting a query to make it more efficient. This can involve | ||
| changing the order of operations in the query or rewriting the query to use a different | ||
| algorithm.</p> | ||
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| <h3>Query Decomposition</h3> | ||
| <p>Query decomposition is the process of breaking a complex query into smaller, simpler queries that | ||
| can be executed more efficiently. This can be done by using subqueries or by rewriting the query | ||
| to eliminate unnecessary operations.</p> | ||
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| <h3>Query Compilation</h3> | ||
| <p>Query compilation is the process of compiling a query into an executable form that can be | ||
| executed by the database engine. This can involve optimizing the query plan and generating | ||
| efficient code to execute the query.</p> | ||
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| <h3>Query Execution</h3> | ||
| <p>Query execution is the process of executing the compiled query and returning the results to the | ||
| user. This can involve reading data from disk, processing the data, and returning the results to | ||
| the user.</p> | ||
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| </div> | ||
| </div> | ||
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| <div id="normalization_and_denormalization" class="id_topic"> | ||
| <div class="question"> | ||
| <h2>Normalization and Denormalization</h2> | ||
| <p>Normalization is the process of organizing data in a database. This includes creating tables and | ||
| establishing relationships between those tables according to rules designed both to protect the | ||
| data and to make the database more flexible by eliminating redundancy and inconsistent | ||
| dependency.</p> | ||
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| <h3>Types of Normalization</h3> | ||
| <p>There are several types of normalization:</p> | ||
| <ul> | ||
| <li>- First Normal Form (1NF)</li> | ||
| <li>- Second Normal Form (2NF)</li> | ||
| <li>- Third Normal Form (3NF)</li> | ||
| <li>- Boyce-Codd Normal Form (BCNF)</li> | ||
| <li>- Fourth Normal Form (4NF)</li> | ||
| <li>- Fifth Normal Form (5NF)</li> | ||
| </ul> | ||
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| <h3>First Normal Form (1NF)</h3> | ||
| <p>First Normal Form (1NF) is the first step in the normalization process. It requires that the | ||
| table | ||
| have a primary key and that each column in the table contain only atomic values.</p> | ||
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| <h3>Second Normal Form (2NF)</h3> | ||
| <p>Second Normal Form (2NF) requires that the table be in 1NF and that all non-key attributes be | ||
| fully | ||
| functionally dependent on the primary key.</p> | ||
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| <h3>Third Normal Form (3NF)</h3> | ||
| <p>Third Normal Form (3NF) requires that the table be in 2NF and that all non-key attributes be | ||
| non-transitively dependent on the primary key.</p> | ||
|
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| <h3>Boyce-Codd Normal Form (BCNF)</h3> | ||
| <p>Boyce-Codd Normal Form (BCNF) requires that the table be in 3NF and that all determinants be | ||
| candidate keys.</p> | ||
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| <h3>Fourth Normal Form (4NF)</h3> | ||
| <p>Fourth Normal Form (4NF) requires that the table be in BCNF and that there be no multi-valued | ||
| dependencies.</p> | ||
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| <h3>Fifth Normal Form (5NF)</h3> | ||
| <p>Fifth Normal Form (5NF) requires that the table be in 4NF and that there be no join dependencies | ||
| on any subset of the candidate key.</p> | ||
|
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| <h3>Denormalization</h3> | ||
| <p>Denormalization is the process of adding redundant data to a database to improve read | ||
| performance. | ||
| This can involve adding redundant columns to a table or duplicating data in multiple tables.</p> | ||
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| </div> | ||
| </div> | ||
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| </div> | ||
| </div> | ||
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| <div class="right-content-navigator rightnav"> | ||
| <div class="navigator"> | ||
| <a href="#" class="nav-link active">Indexes in SQL</a> | ||
| <a href="#" class="nav-link">Query Optimization Techniques</a> | ||
| <a href="#" class="nav-link">Normalization and Denormalization</a> | ||
| </div> | ||
| </div> | ||
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| <script src="../js/script.js"></script> | ||
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| </body> | ||
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