ORACLE的DML语句中可以指定RETURNING INTO语句。RETURNING INTO语句的使用在很多情况下可以简化PL/SQL编程,少一次select into语句。
DELETE操作:RETURNING返回的是DELETE之前的结果;
INSERT操作:RETURNING返回的是INSERT之后的结果;
UPDATE操作:的RETURNING语句是返回UPDATE操作之后的结果。
-- Created on 2015/11/5 星期四 by YANCONG-ZHANG -- Returning的用法 DECLARE -- Local variables here i INTEGER; l_tid NUMBER; l_tname VARCHAR2(200); l_tage NUMBER; BEGIN -- Test statements here --返回要插入的数据 INSERT INTO zyc VALUES (4, 'wy', 20) RETURNING tid, tname, tage INTO l_tid, l_tname, l_tage; dbms_output.put_line(l_tid || '-' || l_tname || '-' || l_tage); --返回要删除的数据 DELETE zyc WHERE tid = 1 RETURNING tid, tname, tage INTO l_tid, l_tname, l_tage; dbms_output.put_line(l_tid || '-' || l_tname || '-' || l_tage); --返回要更新的数据 UPDATE zyc SET tid = 5, tname = 'lwj', tage = 22 WHERE tid = 2 RETURNING tid, tname, tage INTO l_tid, l_tname, l_tage; dbms_output.put_line(l_tid || '-' || l_tname || '-' || l_tage); COMMIT; END;

MySQL'sBLOBissuitableforstoringbinarydatawithinarelationaldatabase,whileNoSQLoptionslikeMongoDB,Redis,andCassandraofferflexible,scalablesolutionsforunstructureddata.BLOBissimplerbutcanslowdownperformancewithlargedata;NoSQLprovidesbetterscalabilityand

ToaddauserinMySQL,use:CREATEUSER'username'@'host'IDENTIFIEDBY'password';Here'showtodoitsecurely:1)Choosethehostcarefullytocontrolaccess.2)SetresourcelimitswithoptionslikeMAX_QUERIES_PER_HOUR.3)Usestrong,uniquepasswords.4)EnforceSSL/TLSconnectionswith

ToavoidcommonmistakeswithstringdatatypesinMySQL,understandstringtypenuances,choosetherighttype,andmanageencodingandcollationsettingseffectively.1)UseCHARforfixed-lengthstrings,VARCHARforvariable-length,andTEXT/BLOBforlargerdata.2)Setcorrectcharacters

MySQloffersechar, Varchar, text, Anddenumforstringdata.usecharforfixed-Lengthstrings, VarcharerForvariable-Length, text forlarger text, AndenumforenforcingdataAntegritywithaetofvalues.

Optimizing MySQLBLOB requests can be done through the following strategies: 1. Reduce the frequency of BLOB query, use independent requests or delay loading; 2. Select the appropriate BLOB type (such as TINYBLOB); 3. Separate the BLOB data into separate tables; 4. Compress the BLOB data at the application layer; 5. Index the BLOB metadata. These methods can effectively improve performance by combining monitoring, caching and data sharding in actual applications.

Mastering the method of adding MySQL users is crucial for database administrators and developers because it ensures the security and access control of the database. 1) Create a new user using the CREATEUSER command, 2) Assign permissions through the GRANT command, 3) Use FLUSHPRIVILEGES to ensure permissions take effect, 4) Regularly audit and clean user accounts to maintain performance and security.

ChooseCHARforfixed-lengthdata,VARCHARforvariable-lengthdata,andTEXTforlargetextfields.1)CHARisefficientforconsistent-lengthdatalikecodes.2)VARCHARsuitsvariable-lengthdatalikenames,balancingflexibilityandperformance.3)TEXTisidealforlargetextslikeartic

Best practices for handling string data types and indexes in MySQL include: 1) Selecting the appropriate string type, such as CHAR for fixed length, VARCHAR for variable length, and TEXT for large text; 2) Be cautious in indexing, avoid over-indexing, and create indexes for common queries; 3) Use prefix indexes and full-text indexes to optimize long string searches; 4) Regularly monitor and optimize indexes to keep indexes small and efficient. Through these methods, we can balance read and write performance and improve database efficiency.


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mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
