Creating an index on multiple columns example The following example creates an index on both last name and first name columns: CREATEINDEXmembers_name_iONmembers(last_name,first_name);Code language:SQL (Structured Query Language)(sql) The following query finds members whose last name starts with ...
Because of the searchmechanism for unique key constraints on multiple columns, you cannot haveidentical values in the non-null columns of a partially null composite uniquekey constraint. 二. 相关测试 2.1 测试unique index 和 uniqueconstraint SYS@anqing2(rac2)> create table ut(idnumber,phone varchar...
Because of the searchmechanism for unique key constraints on multiple columns, you cannot haveidentical values in the non-null columns of a partially null composite uniquekey constraint. 二. 相关测试 2.1 测试unique index 和 uniqueconstraint SYS@anqing2(rac2)> create table ut(idnumber,phone varchar...
其中:1=2(对表作完全计算所花的时间相当于做全表扫描)analyze table table_name compute statistics;Analyze index|cluster indexname estimate statistics;--2分析表的所有字段,所有索引,所有索引字段。其中:1=2analyze table table_name compute statisticsfortableforall indexesforall columns;--3只分析所有有索引...
Analyze index|cluster indexname estimate statistics; ANALYZE TABLE tablename COMPUTE STATISTICS FOR TABLE FOR ALL [LOCAL] INDEXES FOR ALL [INDEXED] COLUMNS; ANALYZE TABLE tablename DELETE STATISTICS ANALYZE TABLE tablename VALIDATE REF UPDATE
A function-based index is just like a standard B*-tree index, except that you can base the index on the result of a SQL function, rather than just on the value of a column or columns. Prior to Oracle8i, if you wanted to select on the result of a function, Oracle retrieved every ...
Function-based indexes, where the index contains the result of a function on the underlying data columns, have no direct equivalent in Azure Synapse. We recommend that you first migrate the data, then in Azure Synapse run the Oracle queries that use function-based indexes to gauge perfo...
However, unique ID numbers are easier to maintain in a relational database application because only one column is required for the ID number, while multiple columns would be required for an intelligent key (one for each section or segment of the code). The Oracle E-Business Suite products ...
Nonunique indexes permit duplicates values in the indexed column or columns. For example, the first_name column of the employees table may contain multiple Mike values. For a nonunique index, the rowid is included in the key in sorted order, so n...
For this reason, the JDBC driver does not report TABLE_REMARKS columns by default. You can enable TABLE_REMARKS reporting by passing a TRUE argument to the setRemarksReporting() method of an OracleConnection object. If you are using a standard java.sql.Connection object, you must cast it to...