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Technical Articles

Database

ORA-01017: invalid username/password; logon denied

When encountering an ORA-01017 error, it means that the login is denied. The main reason is that the user name or password is wrong or the account status is abnormal. 1. First, manually check the user name and password, and note that the upper and lower case and special characters must be wrapped in double quotes; 2. Confirm that the connected service name or SID is correct, and you can connect through tnsping test; 3. Check whether the account is locked or the password expires, and the DBA needs to query the dba_users view to confirm the status; 4. If the account is locked or expired, you need to execute the ALTERUSER command to unlock and reset the password; 5. Note that Oracle11g and above versions are case-sensitive by default, and you need to ensure that the input is accurate. 6. When logging in to special users such as SYS, you should use the assysdba method to ensure the password.

Aug 16, 2025 pm 01:04 PM

database 登錄錯(cuò)誤

How to find my phpMyAdmin URL

Forlocaldevelopment(XAMPP,WAMP,MAMP),accessphpMyAdminviahttp://localhost/phpmyadminorhttp://localhost:8888/phpmyadminforMAMP;2.Onsharedhosting,logintocPanel,gotothe"Databases"section,andclick"phpMyAdmin"toopenitautomatically;3.Ona

Aug 16, 2025 pm 12:35 PM

How to find tables with a specific column name in MySQL?

To find a table containing a specific column name, you should query the INFORMATION_SCHEMA.COLUMNS table; execute SELECTTABLE_NAMEFROMINFORMATION_SCHEMA.COLUMNSWHERECOLUMN_NAME='your_column_name'ANDTABLE_SCHEMA='your_database_name'; you can find all tables containing that column in the specified database, such as looking for tables containing an email column in sales_db; to search across all databases, omit the TABLE_SCHEMA condition and select to return TABLE_NAME at the same time.

Aug 16, 2025 am 11:29 AM

How to pivot data in MySQL (rows to columns)?

To implement row-to-column conversion (i.e. pivot table) in MySQL, conditional aggregation is required to be combined with GROUPBY; 1. Use SUM (CASE...) or MAX (CASE...) combined with GROUPBY to convert row data into columns, which is suitable for known column values; 2. When the column value is not fixed, dynamic SQL is generated through GROUP_CONCAT and executed with PREPARE, pay attention to adjusting group_concat_max_len; 3. IF can be used to replace CASE to simplify syntax, but CASE is still recommended; always use aggregate function, missing values are filled with 0 or NULL, text data is MAX instead of SUM, and finally perspective is completed through grouping and conditional logic.

Aug 16, 2025 am 10:54 AM

How to implement pagination in MySQL

Using LIMIT and OFFSET is the basic method of MySQL paging, which is suitable for small and medium-sized data volumes; for large-scale data or deep paging, index column-based key set paging (such as WHEREid>last_seen_id) should be used to improve performance. Both methods need to ensure the consistency of sorting through ORDERBY. The final choice depends on whether the application scenario needs random page jumps or supports infinite scrolling.

Aug 16, 2025 am 10:50 AM

How to get the last inserted ID in MySQL?

To get the last inserted ID in MySQL, you should use the LAST_INSERT_ID() function. This function returns the last self-increment ID in the current session after insertion. It has session security and is not affected by other clients. It can still obtain the correct result even after executing other queries. If no insertion occurs, it will return 0. For multi-line insertion, return the first generated ID, such as executing INSERTINTOusers(name,email)VALUES('JohnDoe','john@example.com'); followed by SELECTLAST_INSERT_ID(); to obtain the ID of the newly inserted user. When using PHP, you can use $mysqli-&

Aug 16, 2025 am 10:38 AM

mysql

How to use MATCH() AGAINST() for full-text search in MySQL

FULLTEXT index must be created for the text column first, otherwise MATCH()...AGAINST() will report an error; 2. After creating the index, you can use natural language mode, Boolean mode or query extension to search. The natural language mode is sorted by correlation by default. Boolean mode supports operators such as , -, "", *, etc., and query extensions can automatically include related words; 3. Note that MySQL ignores words and common stop words with less than 4 characters by default, and only MyISAM and InnoDB (5.6) support it; 4. To improve performance, FULLTEXT index should be used on text columns to avoid using MATCH() in complex expressions, and Boolean mode is preferred for large data sets, and finally

Aug 16, 2025 am 10:30 AM

How to create a stored procedure in MySQL

To create MySQL stored procedures, you need to use the CREATEPROCEDURE statement and process the delimiter correctly; 1. Use DELIMITER$$ to change the delimiter; 2. Create stored procedures with parameters (IN, OUT, INOUT), including SQL logic in BEGIN...END; 3. Use DELIMITER; restore the delimiter; 4. Use CALL statement to call stored procedures; 5. Complex logic can be implemented in combination with IF, WHILE and other control structures; 6. It is recommended to use DROPPROCEDUREIFEXISTS to avoid duplicate errors; 7. Keep the naming clear and add comments to improve readability. After the entire process is completed, the stored procedure can be successfully created and called.

Aug 16, 2025 am 10:26 AM

mysql stored procedure

How to handle errors in SQL?

SQL error handling requires selecting the corresponding mechanism according to the database system. 1. Use TRY-CATCH block (such as SQLServer) to catch exceptions; 2. Ensure data consistency through transaction combination rollback; 3. Verify data before execution to prevent constraint conflicts; 4. Use functions such as ERROR_MESSAGE() to diagnose errors; 5. Use EXCEPTION block to handle specific exceptions; 6. Define error handlers in MySQL through DECLAREHANDLER; 7. Record error logs to facilitate troubleshooting; 8. Avoid silent failures, and return status codes or notify applications. The ultimate goal is to ensure data integrity and provide clear feedback.

Aug 16, 2025 am 10:20 AM

How to choose between temp tables and table variables in SQL

Usetablevariablesforsmall,simple,short-livedoperationswithminimalindexingneeds,astheyarelightweight,automaticallycleanedup,anddonotcauserecompilation,whileusetemptablesforlargerdatasetsrequiringindexes,statistics,andcomplexoperations,sincetheysupport

Aug 16, 2025 am 09:50 AM

What is the purpose of the foreign key ON DELETE CASCADE in MySQL?

ThepurposeoftheONDELETECASCADEoptioninaforeignkeyconstraintinMySQListoautomaticallydeleterowsinachildtablewhenthecorrespondingrowintheparenttableisdeleted,ensuringreferentialintegritybypropagatingdeletionsfromtheparenttothechildtable;forexample,delet

Aug 16, 2025 am 09:47 AM

SQL Vulnerability Assessment Tools

Common SQL vulnerability assessment tools include SQLMap, Microsoft SQLServerVulnerabilityAssessment(VA), DBProtect, and SentinelDB. SQLMap is good at detecting SQL injection vulnerabilities. Microsoft VA is suitable for SQL Server teams for compliance checks. DBProtect is suitable for enterprise-level multi-database environments. SentinelDB is suitable for regular scanning of small and medium-sized teams. These tools can detect problems such as weak passwords, improper permission configuration, unpatched, unsafe configuration, and exposed sensitive data. When selecting a tool, database type, team size and budget, functional requirements and ease of use should be considered

Aug 16, 2025 am 09:40 AM

How to join a table to itself in SQL

Aself-joinisusedtocomparerowswithinthesametable,suchasinhierarchicaldatalikeemployee-managerrelationships,bytreatingthetableastwoseparateinstancesusingaliases,asdemonstratedwhenlistingemployeesalongsidetheirmanagers'nameswithaLEFTJOINtoincludetop-lev

Aug 16, 2025 am 09:37 AM

sql Self-connection

How Do I Troubleshoot Navicat Connection Errors?

TotroubleshootNavicatconnectionerrors,startbycheckingbasicconnectionparameters,thenaddressnetwork,firewall,server-side,andNavicat-specificissues:1)Verifyserveraddress,port,username,andpassword;2)Checknetworkconnectivityandfirewallsettings;3)Ensurecor

Aug 16, 2025 am 09:23 AM