oraclesql基礎知識論述(文件)
【正文】 ion_id, department_name Department, to_char(null) Warehousefrom departmentsunionselect location_id, to_char(null) Department, warehouse_namefrom warehouses。?About SQL Expressions?Simple Expressions?Compound Expressions ?CASE Expressions ?CURSOR Expressions ?Datetime Expressions?Function Expressions ?INTERVAL Expressions?Object Access Expressions ?Scalar Subquery Expressions?Type Constructor Expressions?Variable Expressions?Expression Lists?About SQL Conditions?Comparison Conditions ?Logical Conditions?Membership Conditions?Range Conditions?Null Conditions ?EXISTS Conditions ?LIKE Conditions SQL DDL子句?allocate_extent_clause?constraints?deallocate_unused_clause?file_specification?logging_clause?parallel_clause?physical_attributes_clause?storage_clause使用在 :alter table,alter index使用在 :alter table,alter index使用在 :create tablespace,create temporary tablespaceAutoextend_clause:使用在 :create table,create index使用在 :create tablespace,create table,create indexExtent_management_clause::=Segment_management_clause::=(只有永久的 ,本地管理的表空間才有關的 )create_temporary_tablespace::=temp_tablespace_extent::=Table_index_clause::=. SQL查詢和子查詢?About Queries and Subqueries?Creating Simple Queries ?Hierarchical Queries ?The UNION [ALL], INTERSECT, MINUS Operators?Sorting Query Results?Joins?Using Subqueries?Unnesting of Nested Subqueries ?Selecting from the DUAL Table?Distributed QueriesA join is a query that bines rows from two or more tables, views, or materialized views. Oracle performs a join whenever multiple tables appear in the query39。 works for 39。 ?right outer joinSELECT , FROM departments d RIGHT OUTER JOIN employees e ON = ORDER BY 。 演講完畢，謝謝觀看！。 A subquery answers multiplepart questions. For example, to determine who works in Taylor39。R%39。s select list can select any columns from any of these tables. If any two of these tables have a column name in mon, then you must qualify all references to these columns throughout the query with table names to avoid ambiguity.Join condition:Most join queries contain WHERE clause conditions that pare two columns, each from a different table. Such a condition is called a join condition. To execute a join, Oracle bines pairs of rows, each containing one row from each table, for which the join condition evaluates to TRUE. The columns in the join conditions need not also appear in the select list.(1)EquijoinsSELECT last_name, job_id, , department_name FROM employees, departments WHERE = 。INTERSECTSELECT product_id FROM inventoriesINTERSECTSELECT product_id FROM order_items。INTERSECTSELECT product_id FROM inventoriesINTERSECTSELECT product_id FROM order_items。有關詳細信息，請參閱專用于該操作系統(tǒng)的 OracleTABLE? 糾正錯誤。? 使用 EXCEPTIONSTABLEVALIDATE選項為缺省設置，不需要在啟用被禁用約束時指定。]EXCEPTIONSINDEX)[,|constraintENABLE[執(zhí)行的約束將保證在驗證期間不會出現(xiàn)違反約束的情況。當啟用不可延遲的主鍵約束或唯一性約束時， Oracle 服務器將創(chuàng)建一個唯一索引。 2 2啟用 VALIDATE約束后將檢查現(xiàn)有數(shù)據(jù)中是否違反約束。? 約束被創(chuàng)建為禁用。INDEX子句僅適用于創(chuàng)建為可延遲的主鍵約束或唯一性約
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