MySQL FLUSH 语句

MySQL 中的 FLUSH 语句用于清除缓存。

语法

以下是 MySQL FLUSH 语句的语法 -

FLUSH [NO_WRITE_TO_BINLOG | LOCAL] {
   BINARY LOGS | ENGINE LOGS | ERROR LOGS | GENERAL LOGS | HOSTS | 
   LOGS | 
   PRIVILEGES | OPTIMIZER_COSTS | RELAY LOGS | SLOW LOGS | STATUS | 
   USER_RESOURCES
}

以下是各种(选项)FLUSH 语句 -

FLUSH BINARY LOGS;

FLUSH ENGINE LOGS;

FLUSH ERROR LOGS;

FLUSH GENERAL LOGS;

FLUSH HOSTS;

FLUSH LOGS;

FLUSH PRIVILEGES;

FLUSH OPTIMIZER_COSTS;

FLUSH RELAY LOGS;

FLUSH STATUS;

FLUSH USER_RESOURCES;

FLUSH TABLES 语句

使用 FLUSH TABLES 语句，您可以刷新表中的数据或获取锁。

语法

以下是 FLUSH TABLES 语句的语法 -

FLUSH TABLES {
   tbl_name [, tbl_name] ...
   | WITH READ LOCK
   | tbl_name [, tbl_name] ... WITH READ LOCK
   | tbl_name [, tbl_name] ... FOR EXPORT
}

示例

假设我们创建了一个表，其中包含销售详情以及客户的联系方式，如下所示 -

CREATE TABLE SALES_DETAILS (
   ID INT,
   ProductName VARCHAR(255),
   CustomerName VARCHAR(255),
   DispatchDate date,
   DeliveryTime time,
   Price INT,
   Location VARCHAR(255),
   CustomerAge INT,
   CustomrtPhone BIGINT,
   DispatchAddress VARCHAR(255),
   Email VARCHAR(50)
);

现在，让我们使用 INSERT 语句将 2 条记录插入到上面创建的表中 -

Insert into SALES_DETAILS values
(1, 'Key-Board', 'Raja', DATE('2019-09-01'), TIME('11:00:00'), 7000, 
'Hyderabad', 25, '9000012345', 'Hyderabad  Madhapur', 
'pujasharma@gmail.com');
(2, 'Mobile', 'Vanaja', DATE('2019-03-01'), TIME('10:10:52'), 9000, 
'Chennai', 30, '9000012365', 'Chennai- TNagar', 'vanajarani@gmail.com');

如果我们想要另一个仅包含客户联系方式的表格，请创建一个表格 -

CREATE TABLE CustContactDetails (
   ID INT,
   Name VARCHAR(255),
   Age INT,
   Phone BIGINT,
   Address VARCHAR(255),
   Email VARCHAR(50)
);

以下查询使用 INSERT INTO SELECT 语句将记录插入到 CustContactDetails 表中。这里，我们尝试将 SALES_DETAILS 表中的记录插入到 CustContactDetails 表中 -

INSERT INTO CustContactDetails (ID, Name, Age, Phone, Address, Email)
SELECT
ID, CustomerName, CustomerAge, CustomrtPhone, DispatchAddress, Email
FROM SALES_DETAILS
WHERE ID = 1 AND CustomerName = 'Raja';

INSERT INTO CustContactDetails (ID, Name, Age, Phone, Address, Email)
SELECT
ID, CustomerName, CustomerAge, CustomrtPhone, DispatchAddress, Email
FROM SALES_DETAILS
WHERE ID = 2 AND CustomerName = 'Vanaja';

您可以验证 CustContactDetails 表的内容，如下所示 -

SELECT * FROM CustContactDetails;

输出

以下是上述查询的输出 -

以下查询集锁定实例，刷新上面创建的表并解锁实例。

LOCK INSTANCE FOR BACKUP;

FLUSH TABLES emp, custcontactdetails WITH READ LOCK;

UNLOCK TABLES;

UNLOCK INSTANCE;