Primary Index是指数据库表中的主索引,Secondary Index是指数据库表中的次要索引。 Primary Index在数据库表中是唯一的,不允许有空值。Secondary Index在数据库表中不是唯一的,允许有空值。©2022 Baidu |由 百度智能云 提供计算服务 | 使用百度前必读 | 文库协议 | 网站地图 | 百度营销
Robinson R, Batisky D, Hayes J, Nahata M, Mahan J (2004) Body mass index in primary and secondary pediatric hypertension. Pediatr Nephrol 19:1379–1384Robinson RF, Batisky DL, Hayes JR, Nahata MC, Mahan JD (2004) Body mass index in primary and secondary pediatric hypertension. Pediatr ...
+ and it must be unique!, if all key fields are use with equal, they specify exactly one record The uniquiness is necessary for a DIRECT read, the primary key MUST be unique, the secondary index can be unique. The used index is determined by the optimizer with the fields given in th...
Bug #56714 Slow MAX() on primary key retrieved by secondary index in InnoDB Submitted: 10 Sep 2010 12:45Modified: 2 Apr 2013 7:20 Reporter: Nicholas Sherlock Email Updates: Status: Closed Impact on me: None Category: MySQL Server: OptimizerSeverity: S5 (Performance) Version: 5.1.50, ...
Description:Currently InnoDB stores "unnecessary" PKV fields into unique secondary index node pages, inflating their size. For a table with a key PRIMARY KEY (a, b, c) and UNIQUE KEY (a, d), InnoDB will store the fields b and c in the node pages of the unique key on (a, d) wher...
I am more curious about this than anything, because most indexing and sorting is done through queries, but in Excel you can sort a range by a primary and secondary field. Can you have a primary and secondayr sort field when you view an Access table or can you only sort one field at...
all DBMS's do not implement primary keys in the same fashion and because of that, if you wanted to create a cross platform, cross application database application, you could not use primary keys, but instead would need to put a unique constraint on the table in place of the pri...
11 primary key fields, 5 secondary key fields and 5 SumIndexFields will cause an error When this limitation is exceeded NAV will generate the following error message when trying to save the table definition: “The fields in an active key may not exceed 252 bytes. The s...
The theme of the 26th National Traffic Safety Day for primary and secondary school students is “Identifying and Avoiding Danger to Secure Safety”. Duolun Technology will keep on passing on the love and power of the “Magic Box” in the future. It will continue supporting public welfare by ...
StatementWithCtesAndXmlNamespaces StatisticsOption StatisticsOptionKind StatisticsPartitionRange StopListFullTextIndexOption StopRestoreOption StringLiteral SubqueryComparisonPredicate SubqueryComparisonPredicateType SymmetricKeyStatement SystemTimePeriodDefinition SystemVersioningTableOption TableClus...