insert into aa values(3, 'c', 3); explain select b from aa where b in ('a','ab'); 可以得到如下的查询执行计划: test=# explain select b from aa where b in ('a','ab'); QUERY PLAN --- Bitmap Heap Scan on aa (cost=8.52..13.86 rows=2 width=38) Recheck Cond: ((b)::tex...
-- -- SQL语句一 使用 EXISTS -- select customerid, companyname from customers as A where country = 'Spain' and not exists ( select * from orders as B where A.customerid = B.customerid ); -- -- SQL语句二 使用 IN -- select customerid, companyname from customers as A where country...
public int delete (Stringtable,StringwhereClause,String[]whereArgs) Convenience method for deleting rows in the database. Parameters Returns the number of rows affected if a whereClause is passed in, 0 otherwise. To remove all rows and get a count pass "1" as the whereClause. 示例: ContentV...
{query-specification|VALUES (insert-value[,insert-value]...)} 請注意,查詢規格元素只在 Core 和 Extended SQL 文法中有效,而且運算式和搜尋條件元素在 Core 和 Extended SQL 文法中也逐漸變得更複雜。 與其他 SQL 陳述式一樣,UPDATE、DELETE和INSERT陳述式在使用參數時,通常會更有效率。 例如,您可以準備並重...
+---+---+---+---+---+---+8rows in set (0.00sec) 2.修改数据 #使用update语句必须要加where条件 mysql> update student set age=18where name='小王';QueryOK,2rows affected (0.01sec)Rowsmatched:2Changed:2Warnings:0mysql> select * from student; +---+---+---+---+---+--...
syntaxsql複製 -- Syntax for Parallel Data WarehouseDELETE[FROM[database_name. [ schema ] . | schema. ]table_name] [WHERE<search_condition>] [OPTION(<query_options>[ ,...n ] ) ] [; ] 引數 WITH <common_table_expression> 指定定義在 DELETE 陳述式範圍內的暫存具名結果集,也稱為一般資料...
PHP使用 mysqli_query() 函数来执行SQL语句, 你可以在 SQL DELETE 命令中使用或不使用 WHERE 子句。该函数与 mysql> 命令符执行SQL命令的效果是一样的。 MySQL DELETE 语句测试以下PHP实例将删除 runoon_tbl 表中 runoon_id 为 3 的记录: <?php$dbhost = ...
OPTION(<query_hint> [,...n]) Keywords that indicate which optimizer hints are used to customize the way the Database Engine processes the statement. For more information, seeQuery Hints (Transact-SQL). Best Practices To delete all the rows in a table, useTRUNCATE TABLE.TRUNCATE TABLEis fas...
SQL(Structured Query Language)简介 SQL(Structured Query Language)是一种用于访问和操作关系型数据库的标准编程语言,是用于数据库查询和程序设计的语言。其主要功能包括数据查询、数据操作、事务控制、数据定义和数据控制等。 SQL具有以下特点: 高级的非过程化编程语言:允许用户在高层数据结构上工作,不需要了解具体的数...
SQLiteDataBase对象的query()接口: publicCursorquery(Stringtable,String[]columns,Stringselection,String[]selectionArgs,StringgroupBy,Stringhaving,StringorderBy,Stringlimit) Query the given table, returning aCursorover the result set. Parameters Returns ...