Found a total of 10000 related content
Can the Bootstrap image be centered in combination with media query?
Article Introduction：Bootstrap provides an easy way to center images, but Media Query can help you control the position of images under different screen sizes. With Media Query, you can adjust the image display according to the device width, or even use different images. Flexible mastery of Bootstrap and Media Query can achieve responsive and beautiful picture layouts, but don't forget to consider vertical centering and performance optimization.
2025-04-07
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802
Polymorphism Types vs Design pattern
Article Introduction：How to use polymorphism and design patterns in combination? The combination of polymorphism and design patterns can enhance the flexibility and maintainability of the code by: 1. The policy pattern uses polymorphism to define the algorithm family, making it interchangeable at runtime; 2. The template method pattern delays the implementation of algorithm steps in the subclass through polymorphism; 3. The visitor pattern uses polymorphism in the form of double-scheduling, allowing new operations to be added in the class hierarchy.
2025-06-21
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236
Understanding SQL Subqueries: A complete guide with examples
Article Introduction：Detailed explanation and examples of SQL subquery What is SQL subquery? Subqueries, also known as internal or nested queries, refer to queries embedded in another SQL query. It is enclosed in brackets, executed before the external query, and provides results for the external query for further processing. Subquery type Single-line subquery: Returns single-line results, usually used in combination with =, etc. comparison operators. Example: Find the name of the highest paid employee: SELECTnameFROMemployeesWHEREssalary=(SELECTMAX(salary)FROMemployees); Multi-line subquery: Returns multi-line results, usually used in combination with operators such as IN, ANY, and ALL. Example: Check
2025-04-08
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325
Beyond the Interface: phpMyAdmin and the Power of SQL
Article Introduction：The combination of phpMyAdmin and SQL allows users to directly enter and execute SQL commands, implementing more complex queries and database management. 1) In phpMyAdmin, you can execute SQL commands, such as SELECTFROMusersWHEREage>30; 2) Use the EXPLAIN command to analyze the execution plan of the query and optimize performance; 3) By creating indexes, avoiding SELECT and using LIMIT, the query efficiency can be significantly improved.
2025-05-02
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716
How to navigate programmatically with vue router?
Article Introduction：Use router.push() to implement programming navigation, and you can jump to the page without clicking on the link. Basic usage includes passing paths or named routes and parameters; calling through useRouter in Composition API; paying attention to avoid errors caused by continuous calls; navigation failures can be handled in combination with .catch(); .replace() can be used for jumps without history; query parameters can be added through query.
2025-07-07
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930
How to use aggregate functions like COUNT, SUM, and AVG in SQL?
Article Introduction：In SQL, COUNT is used to count row counts, SUM is used to add total values, and AVG is used to calculate the average value. 1. COUNT(*) counts all rows, COUNT(column_name) counts non-null values; 2. SUM is often used to sum numerical columns, and can be filtered in combination with WHERE, and can be classified and summarized in combination with GROUPBY; 3. AVG calculates the average value, automatically ignores NULL, and can also be used in combination with conditions and grouping; 4. Multiple aggregate functions can be used at the same time to improve query efficiency and support finer-grained analysis.
2025-07-04
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189
Optimizing MySQL for Content Delivery Networks (CDNs)
Article Introduction：To improve the performance of MySQL in the CDN system, you can start from the following four aspects: 1. Optimize the query statement, avoid SELECT*, use index field query, do not do function operations on fields in the WHERE clause, and analyze the execution plan through EXPLAIN; 2. Set the index reasonably, build indexes on commonly used query fields, use combination indexes to improve efficiency, and clean useless indexes regularly; 3. Use Redis or Memcached to cache high-frequency query results, reduce database pressure, and set a reasonable cache expiration strategy; 4. Adjust the database configuration, such as increasing max_connections, setting innodb_buffer_pool_size, turning on slow query logs, and making
2025-07-18
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581
What are prefix indexes in MySQL and when are they useful/problematic?
Article Introduction：Prefix indexing is a tool in MySQL used to optimize query performance, reducing the index size by indexing the first N characters of a string field. When using prefix indexes, you need to pay attention to: 1. Select the appropriate prefix length, 2. Avoid query conditions involving the middle or back characters of the string, 3. Use in combination with other index types, 4. Regularly monitor and adjust the index strategy.
2025-04-07
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489
MySQL Performance Boosting with Indexes and Explain
Article Introduction：Key Points
Use MySQL's EXPLAIN command to analyze and optimize query execution plans, ensuring more efficient database operations by revealing key information such as connection types and index usage.
Implement query analysis to measure the actual run time of a query, thereby performing targeted optimizations to reduce execution time and improve overall performance.
Add appropriate indexes based on feedback from the EXPLAIN command, focusing on the columns used in the WHERE clause to speed up data retrieval and improve query performance.
For columns involved in search operations, consider using full-text indexing to optimize performance, especially when using the LIKE operator in a query.
Note the use of ORDER BY in combination with LIMIT as it may offset the limit
2025-02-08
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730
SQL Query Hint Usage: When and How to Apply Them
Article Introduction：QueryHint is a tool in SQL query optimization that forces databases to execute queries in a specified manner. It is suitable for unstable performance, existing optimization directions, temporary solutions and specific business needs. Common types include table prompts (such as NOLOCK, READPAST, INDEX), query-level prompts (such as RECOMPILE, MAXDOP, LOOPJOIN) and combination use, but attention should be paid to prioritizing verification in the test environment, monitoring the execution plan, reviewing the effectiveness regularly, and keeping documentation.
2025-07-19
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850
MongoDB advanced query skills to accurately obtain required data
Article Introduction：This article explains the advanced MongoDB query skills, the core of which lies in mastering query operators. 1. Use $and, $or, and $not combination conditions; 2. Use $gt, $lt, $gte, and $lte for numerical comparison; 3. $regex is used for regular expression matching; 4. $in and $nin match array elements; 5. $exists determine whether the field exists; 6. $elemMatch query nested documents; 7. Aggregation Pipeline is used for more powerful data processing. Only by proficiently using these operators and techniques and paying attention to index design and performance optimization can you conduct MongoDB data queries efficiently.
2025-04-12
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962
How to find and optimize slow queries in MySQL?
Article Introduction：Turning on slow query logs, using tool analysis, optimizing specific queries, and regular monitoring are four key steps in optimizing MySQL slow query. First, check and enable slow_query_log through SHOWVARIABLES to set the appropriate long_query_time threshold and log path; secondly, use mysqldumpslow or pt-query-digest to analyze the log location problem SQL; then use EXPLAIN to view the execution plan, focusing on optimizing queries such as missing indexes, large number of scan lines, and file sorting; finally establish a continuous monitoring mechanism and review the logs regularly, and ensure long-term effectiveness in combination with SQL audits before going online.
2025-06-14
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482
Healthcare Data Management with SQL
Article Introduction：SQL improves data management efficiency through standardized design, efficient query and permission control in medical data management. First, patient information, medical records and diagnostic results are stored in the table to reduce redundancy and improve maintainability; second, multi-table connection, conditional filtering and indexing are used to optimize query performance to achieve fast and accurate data retrieval; finally, sensitive data access is restricted through role permission control and view, and data security is ensured in combination with backup and audit.
2025-07-17
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784
