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【判断题】DROP INDEX语句很适合删除通过定义PRIMARY KEY和UNIQUE约束创建的索引
A．Y.是
B．N.否
参考答案和解析
drop index不能删除非聚焦索引
更多 “【判断题】DROP INDEX语句很适合删除通过定义PRIMARY KEY和UNIQUE约束创建的索引A．Y.是B．N.否” 相关考题
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关于索引的叙述,不正确的是()。
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用SQL语句创建表，使用语句 CREATE TABLE 。对列的约束主要有NOT NULL ，UNIQUE，PRIMARY KEY ，FOREIGN KEY 等。定义表的删除与更新操作的完整性约束，主要有四种模式：NO ACTION ，CASCADE ，SET NULL ，SET DEFAULT 。检查列的取值范围可以用 CHECK 约束。设定列的默认取值，可以用DEFAULT 短语。 ()
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根据SQL标准，要创建唯一索引该使用下面哪种语句?()A CREATE UNIQUE INDEXB CREATE CLUSTER INDEXC CREATE ONLY INDEXD CREATE PRIMARY INDEX
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要删除mytable表中的myindex索引，可以使用（）语句。A、DROP myindexB、DROP mytable.myindexC、DROP INDEX myindexD、DROP INDEX mytable.myindex
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SQL SERVER数据库中，UNIQUE约束与PRIMARY KEY约束之间的区别是（）A、UNIQUE约束要求数据库表中至少存在一行数据，因此必须在创建数据库表之后才能创建，而PRIMARY KEY约束无此限制B、UNIQUE约束允许存在空值，而PRIMARY KEY约束不允许存在空值C、创建UNIQUE约束之后，该数据行允许被更改，而PRIMARY KEY约束的数据行，不允许更改D、UNIQUE约束列不能创建外键，而PRIMAR YKEY约束列可以创建外键引用
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Which two statements are true about the primary key constraint in a table？ （）A、It is not possible to disable the primary key constraint.B、It is possible to have more than one primary key constraint in a single table.C、The primary key constraint can be referred by only one foreign key constraint.D、The primary key constraint can be imposed by combining more than one column.E、The non-deferrable primary key constraint creates an unique index on the primary key column if it is not already indexed.
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Which two statements are true about constraints? （）A、The UNIQUE constraint does not permit a null value for the column.B、A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.C、The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.D、The NOT NULL constraint ensures that null values are not permitted for the column.
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The InnoDB engine has a feature known as clustered indexes. Which three statements are true about clustered indexes as used in InnoDB?（）A、A primary key must exist for creation of a clustered indexB、A clustered index allows fulltext searching within InnoDBC、The first unique index is always used as a clustered index and not a primary keyD、A clustered index provides direct access to a page containing row dataE、If no indexes exist, a hidden clustered index is generated based on row IDsF、A primary key is used as a clustered indexG、A clustered index is a grouping of indexes from different tables into a global index for faster searching
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单选题View the Exhibit and examine the structure of the EMP table. You executed the following command to add a primary key to the EMP table： ALTER TABLE emp ADD CONSTRAINT emp_id_pk PRIMARY KEY （emp_id） USING INDEX emp_id_idx； Which statement is true regarding the effect of the command？（）A
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考题
单选题SQL SERVER数据库中，UNIQUE约束与PRIMARY KEY约束之间的区别是（）A
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多选题Which two statements are true about constraints? （）AThe UNIQUE constraint does not permit a null value for the column.BA UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.CThe PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.DThe NOT NULL constraint ensures that null values are not permitted for the column.
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多选题Which two statements are true about the primary key constraint in a table？ （）AIt is not possible to disable the primary key constraint.BIt is possible to have more than one primary key constraint in a single table.CThe primary key constraint can be referred by only one foreign key constraint.DThe primary key constraint can be imposed by combining more than one column.EThe non-deferrable primary key constraint creates an unique index on the primary key column if it is not already indexed.
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单选题使用下列SQL语句创建教师表：CREATE TABLE教师表（教师编号I PRIMARY KEY，姓名C（8）NOT NULL，职称C（10）DEFAULT’讲师’）如果要删除“职称”字段的DEFAULT约束，正确的SQL语句是（ ）。A
ALTER TABLE教师表ALTER职称DROP DEFAULTB
ALTER TABLE教师表ALTER职称DELETE DEFAULTC
ALTER TABLE教师表DROP职称DEFAULTD
ALTER TABLE教师表DROP职称
考题
判断题PRIMARY KEY约束和NULL约束不能同时定义在相同的列上。A
对B
错
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