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Technical Articles

Database

SQL for Graph Databases: Neo4j and SQL Integration

Neo4j cannot use SQL directly, but it can be used in combination through integrated methods. Because Neo4j is a graph database and uses the Cypher query language, unlike SQL's relational data model, it operates on nodes and relationships, rather than tables and rows. For example, SQL query users and orders requires JOIN, while Cypher expresses relationships through MATCH. Despite this, Cypher is logically similar to SQL and is not very difficult to learn. In actual projects, Neo4j is often shared with SQL databases. Common integration methods include: 1. Use ETL tools (such as Talend and Neo4jETL) to convert SQL data into graph structures; 2. Connect SQ through scripting languages ??(such as Python)

Sep 10, 2025 am 01:48 AM

How to view table structure details in Navicat?

There are three ways to view the table structure in Navicat: First, by opening the table designer, double-clicking the table name in the left panel or right-clicking the "Design Table" to view columns, data types, constraints, etc.; Second, use the DDL viewer, right-clicking the table to select "DDL" or find the DDL tab in the properties to view the complete CREATETABLE statement; Third, checking the column dependencies and relationships, and viewing the table associations and dependencies in the "Foreign Key" tab or related parts of the properties of the table designer.

Sep 10, 2025 am 01:03 AM

How to reset the root password in phpMyAdmin

YoucannotresettherootpassworddirectlyinphpMyAdminbecauseitisadatabasemanagementinterface,notapasswordmanagementtool;theMySQLrootpasswordmustberesetattheMySQLlevelbyfollowingthesesteps:1.StoptheMySQLserviceusingsudosystemctlstopmysqlorsudosystemctlsto

Sep 10, 2025 am 12:43 AM

root password

How to find overlapping date ranges in SQL

To determine the overlapping date range in SQL, the core condition is: start1start2, which is applicable to partial overlap, complete inclusion or complete match; for example, querying the subscription record with room_id of 101 and overlapping with the '2025-04-10' to '2025-04-15' time period, you can use SELECT*FROMbookingsWHEREroom_id=101ANDstart_date'2025-04-10'; if you need to find all overlapping date pairs in the table, you can use self-join and add a.id

Sep 09, 2025 am 06:52 AM

sql 重疊日期范圍

How to create a temporary table in MySQL

To create a MySQL temporary table, use the CREATETEMPORARYTABLE statement; 1. The temporary table is only visible in the current session and automatically deletes when the session ends; 2. It can have the same name as the permanent table, and the temporary table is preferred within the session; 3. Use standard statements such as INSERT and SELECT to operate the data; 4. The temporary table can be manually deleted through DROPTEMPORARYTABLE to avoid accidentally deleting permanent tables.

Sep 09, 2025 am 05:06 AM

How to use prepared statements in MySQL?

The use of preprocessing statements can effectively prevent SQL injection and improve the performance of multiple queries. It is separated from the SQL structure and data, first implemented using PREPARE, SET, EXECUTE and DEALLOCATE commands in MySQL, or implemented in programming languages ??such as PHP, Python, Java, etc. through preprocessing mechanisms supported by drivers such as PDO, mysql-connector-python, JDBC. The placeholder (? or named parameters) can only represent values ??and cannot be used for table names, column names or SQL keywords. In the IN clause, placeholders need to be set separately for each value. This method has the advantages of high security, excellent performance and clear code, and has become the best database operation.

Sep 09, 2025 am 04:57 AM

Building Recursive Queries with SQL CTEs

RecursivequeriesinSQLarebuiltusingrecursiveCommonTableExpressions(CTEs)tohandlehierarchicaldata.1.Startwithananchormemberselectingroot-leveldata.2.AddarecursivememberthatreferencestheCTEtotraversethehierarchy.3.CombinebothpartsusingUNIONALL.Forexampl

Sep 09, 2025 am 04:38 AM

recursive query SQL CTE

What is the difference between ZREM and ZREMRANGEBYSCORE?

The difference between ZREM and ZREMRANGEBYSCORE is that the deletion method is different. 1. ZREM is deleted by member, used to remove one or more designated members, and does not care about their scores, and is suitable for deleting specific users or cheating entries; 2. ZREMRANGEBYSCORE is deleted by fraction range, suitable for batch cleaning of low-score or expired data, and supports open and closed intervals; both support multiple deletion and no errors are reported, but it is recommended to execute during low peak periods when deleting a large amount of data in performance.

Sep 09, 2025 am 04:10 AM

redis

How to handle character encoding issues like UTF8 in MySQL?

The utf8mb4 character set must be used to ensure that MySQL correctly handles UTF-8 encoding, including emoji and multilingual characters, because MySQL's utf8 is a pseudo-UTF-8, which only supports up to 3 byte characters and cannot store 4 byte characters; while utf8mb4 supports complete UTF-8 encoding, so CHARACTERSETutf8mb4COLLATEutf8mb4_unicode_ci should be explicitly set at the database, table, and column levels to obtain accurate sorting and comparison capabilities; at the same time, the default character set of client, mysql and mysqld parts must be set to utf8mb4 in the MySQL configuration file, and the client character set handshake should be skipped to strengthen the

Sep 09, 2025 am 04:04 AM

mysql utf8

How to perform union and intersection on Sorted Sets? (ZUNIONSTORE, ZINTERSTORE)

How to handle union and intersection of SortedSet in Redis? Use the ZUNIONSTORE and ZINTERSTORE commands to calculate the union and intersection of multiple ordered sets, and store the results in a new key; 1. ZUNIONSTORE is used for union, and the score of each member is the sum of its scores in each set by default. Weights can be set through WEIGHTS, and AGGREGATE specifies the aggregation method (SUM, MIN, MAX); 2. ZINTERSTORE is used for intersection, and only all members that exist in the specified set are retained, and the scores are aggregated according to the configuration; 3. Both commands can set weights and aggregation methods, which are suitable for ranking mergers, multi-dimensional data filtering and other scenarios.

Sep 09, 2025 am 03:37 AM

How to set up replication in MySQL

Configure the server-id of the master server, enable binary logs and set log format; 2. Create a dedicated user for replication and grant permissions; 3. Configure the unique server-id of the slave server; 4. Get the binary log file name and location on the master server; 5. Execute the CHANGEREPLICATIONSOURCETO command on the slave server and start replication; 6. Verify the replication status through SHOWREPLICASTATUS to ensure that the IO and SQL threads run normally and have no errors; 7. If the master library already has data, it needs to be exported using mysqldump and imported into the slave library to ensure data consistency, and finally realize master-slave data synchronization.

Sep 09, 2025 am 03:34 AM

How to optimize LIKE queries with a leading wildcard in MySQL

Use reverse index to convert suffix searches into prefix searches, thereby improving performance using indexes; 2. For word-based searches, use FULLTEXT index to achieve efficient full-text search; 3. Use generated columns to pre-calculate and index the query values ??of fixed patterns in MySQL5.7; 4. For complex partial matching or frequent search requirements, external search engines such as Elasticsearch are used; 5. Optimize queries by combining index conditions, limiting the return results, and using overlay indexes to reduce the impact of full table scanning.

Sep 09, 2025 am 03:22 AM

Performance Tuning for High Throughput Writes in MongoDB

Use unordered batch writes (bulkWritewithordered:false) to improve write efficiency; 2. If the risk of data loss is acceptable, disable logs (j:false or global shutdown journal) to reduce I/O overhead; 3. Tune the WiredTiger storage engine to increase cache, enable compression and pre-slice to avoid hotspots; 4. Simplify the indexing strategy, create only necessary indexes to avoid excessive indexes to slow down writes; 5. Realize horizontal scaling through hash sharding, and distribute the write load to support high throughput. The core of optimization lies in batch processing, reducing persistence requirements, rationally configuring storage, controlling the number of indexes and timely sharding, thereby maximizing MongoDB write performance and ultimately achieving stable and efficient write-intensive w

Sep 09, 2025 am 03:01 AM

mongodb Performance optimization

How to sort by a custom order in SQL

Use CASE expressions to implement custom sorting in SQL. 1. Use ORDERBY and CASE to assign sorting weights to each value, which is suitable for all mainstream databases; 2. Use FIELD() function to simplify the syntax in MySQL, but the values ??that are not in the list need to be processed; 3. It is recommended to use ARRAY_POSITION() instead of POSITION() in PostgreSQL to avoid matching errors; 4. For frequently used sorting logic, it is easier to maintain for creating mapping tables and associated queries. This method ensures that the custom order takes effect accurately and supports multi-column sorting and outlier processing, ultimately achieving flexible and reliable sorting results.

Sep 09, 2025 am 02:55 AM