MySQL – Repair Tables


MySQL – Repair Tables


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MySQL Repair Table Statement

There can be scenarios where tables in databases can become corrupted due to various reasons such as hardware failures, software bugs, or unexpected server crashes. When this situation happens, we cannot be able to access or manipulate the data in those tables because of data inconsistencies or errors.

In such situations, to repair those currupted tables, we use the MySQL REPAIR TABLE statement. This statement works for only certain engines such as MyISAM, etc.

Syntax

Following is the syntax of MySQL REPAIR TABLE Statement −


REPAIR [NO_WRITE_TO_BINLOG | LOCAL]
   TABLE tbl_name [, tbl_name] ...
   [QUICK] [EXTENDED] [USE_FRM]

Example

Let us start by creating a table named CUSTOMERS using the following query −


CREATE TABLE CUSTOMERS (
   ID INT AUTO_INCREMENT,
   NAME VARCHAR(20) NOT NULL,
   AGE INT NOT NULL,
   ADDRESS CHAR (25),
   SALARY DECIMAL (18, 2),
   PRIMARY KEY (ID)
);

Here, we are inserting 7 records into the above created table using the below INSERT statement −


INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY) VALUES 
(1, ''Ramesh'', 32, ''Ahmedabad'', 2000.00 ),
(2, ''Khilan'', 25, ''Delhi'', 1500.00 ),
(3, ''Kaushik'', 23, ''Kota'', 2000.00 ),
(4, ''Chaitali'', 25, ''Mumbai'', 6500.00 ),
(5, ''Hardik'', 27, ''Bhopal'', 8500.00 ),
(6, ''Komal'', 22, ''Hyderabad'', 4500.00 ),
(7, ''Muffy'', 24, ''Indore'', 10000.00 );

Assume the above created table is corrupted and we are using the REPAIR TABLE statement to repair it.


REPAIR TABLE CUSTOMERS;

The above query displays an error as: “The storage engine for the table doesn”t support repair” because the REPAIR TABLE statement won”t work with the default InnoDB engine.




Table Op Msg_type Msg_text
tutorials.customers repair note The storage engine for the table doesn”t support repair

To repair the table, We need to change the table”s engine to MyISAM because it supports the REPAIR TABLE statement.


ALTER TABLE CUSTOMERS ENGINE = MyISAM;

Now, to repair the CUSTOMERS table, execute the following query −


REPAIR TABLE CUSTOMERS;

Output

We can see in the output below, it says OK which indicates that the table CUSTOMERS is in good condition, and there are no issues or corruption.




Table Op Msg_type Msg_text
tutorials.customers repair status OK

Repairing multiple tables

In MySQL, we can also repair multiple tables and get the results using the REPAIR TABLE Statement. To do this, we just need to list the names of the tables we want to repair, separating them with commas.

Example

Let us create three different tables with the names Test1, Test2, and Test3 using the following CREATE TABLE statements −


CREATE TABLE Test1(ID INT, Name VARCHAR(255));
CREATE TABLE Test2(ID INT, Name VARCHAR(255));
CREATE TABLE Test3(ID INT, Name VARCHAR(255));

Assume the above three tables are corrupted. Change the engine of these tables to MyISAM to repair them with REPAIR TABLE statement −


ALTER TABLE Test1 ENGINE = MyISAM;
ALTER TABLE Test2 ENGINE = MyISAM;
ALTER TABLE Test3 ENGINE = MyISAM;

Now, to repair these tables, execute the following query −


REPAIR TABLE Test1, Test2, Test3;

As we can see in the output below, all three tables are in good condition, and there are no issues or corruption.






Table Op Msg_type Msg_text
tutorials.test1 repair status OK
tutorials.test2 repair status OK
tutorials.test3 repair status OK

Repair Table Options

We have various optional clauses to use with REPAIR TABLE such as QUICK, EXTENDED, and, USE_FRM clause. Let us discuss them one by one with suitable examples.

QUICK Clause

The QUICK clause is the is the default and it is most commonly used with REPAIR TABLE. If you specify the QUICK clause, MySQL will repair the table without re-creating it. −


Example

In the following example, we are using the QUICK clause with the REPAIR TABLE statement to repair the CUSTOMERS table.


REPAIR TABLE CUSTOMERS QUICK;


Output

Executing the query above will produce the following output −




Table Op Msg_type Msg_text
tutorials.customers repair status OK

EXTENDED Clause

If we specify the EXTENDED clause, MySQL not only repairs the table but also rebuilds the index and optimizes the table structure.

Note: The EXTENDED clause is a more time-consuming compared to QUICK clause.


Example

In the following example, we are using the EXTENDED clause with the REPAIR TABLE statement to repair the CUSTOMERS table. 


REPAIR TABLE CUSTOMERS EXTENDED;


Output

Executing the query above will produce the following output −




Table Op Msg_type Msg_text
tutorials.customers repair status OK

USE_FRM clause

We can use the USE_FRM clause, in case the MYI index file is missing. If you provide this clause the .NYI file will be recreated using information from the data dictionary −


Example

Here, we are using the USE_FRM clause with the REPAIR TABLE statement to repair the CUSTOMERS table.


REPAIR TABLE CUSTOMERS USE_FRM;


Output

Executing the query above will produce the following output −





Table Op Msg_type Msg_text
tutorials.CUSTOMERS repair warning Number of rows changed from 0 to 7
tutorials.customers repair status OK


Repairing table Using a Client Program

Besides repairing a table in a MySQL database with a MySQL query, we can also use a client program to perform the REPAIR TABLE operation.

Syntax

Following are the syntaxes to repair a table in various programming languages −


PHP
NodeJS
Java
Python

To repair a table in a MySQL Database through a PHP program, we need to execute the Repair Table statement using the mysqli function query() as −


$sql="Repair TABLE table_names";
$mysqli->query($sql);

To repair a table in a MySQL Database through a Node.js program, we need to execute the Repair Table statement using the query() function of the mysql2 library as −


sql=" REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [, tbl_name] ...
   [QUICK] [EXTENDED] [USE_FRM]";
con.query(sql);

To repair a table in a MySQL database through a Java program, we need to execute the Repair Table statement using the JDBC function executeUpdate() as −


String sql="Repair TABLE table_names";
statement.executeUpdate(sql);

To repair a table in a MySQL database through a Python program we need to execute the Repair Table statement using the execute() function of the MySQL Connector/Python as −


sql="REPAIR TABLE table_name";
cursorObj.execute(sql);

Example

Following are the programs −


PHP
NodeJS
Java
Python 


$dbhost = ''localhost'';
$dbuser = ''root'';
$dbpass = ''password'';
$dbname = ''TUTORIALS'';
$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);

if ($mysqli->connect_errno) {
    printf("Connect failed: %s
", $mysqli->connect_error);
    exit();
}
// printf(''Connected successfully.
'');

$sql = " REPAIR TABLE SalesSummary ";
if ($mysqli->query($sql)) {
    printf(" Table repair successfully.
");
}
if ($mysqli->errno) {
    printf("table could not be repaired .
", $mysqli->error);
}
$mysqli->close();

Output

The output obtained is as follows −


Table repair successfully.



var mysql = require(''mysql2'');
var con = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "Nr5a0204@123"
});

  //Connecting to MySQL
  con.connect(function (err) {
  if (err) throw err;
  console.log("Connected!");
  console.log("--------------------------");

  sql = "Create Database TUTORIALS"
  con.query(sql);

  sql = "USE TUTORIALS"
  con.query(sql);

  sql = "CREATE TABLE sales(ID INT, ProductName VARCHAR(255), CustomerName VARCHAR(255), DispatchDate date, DeliveryTime time, Price INT, Location VARCHAR(255));"
  con.query(sql);

  sql = "insert into sales values(1, ''Key-Board'', ''Raja'', DATE(''2019-09-01''), TIME(''11:00:00''), 7000, ''Hyderabad''),(2, ''Earphones'', ''Roja'', DATE(''2019-05-01''), TIME(''11:00:00''), 2000, ''Vishakhapatnam''),(3, ''Mouse'', ''Puja'', DATE(''2019-03-01''), TIME(''10:59:59''), 3000, ''Vijayawada''),(4, ''Mobile'', ''Vanaja'', DATE(''2019-03-01''), TIME(''10:10:52''), 9000, ''Chennai''),(5, ''Headset'', ''Jalaja'', DATE(''2019-04-06''), TIME(''11:08:59''), 6000, ''Goa'');"
  con.query(sql);

  sql = "ALTER TABLE Sales ENGINE = MyISAM;"
  con.query(sql);

  sql = "REPAIR TABLE Sales;"
  con.query(sql, function(err, result){
    if (err) throw err
    console.log(result);
  });
});

Output

The output produced is as follows −


Connected!
--------------------------
[
  {
    Table: ''tutorials.sales'',
    Op: ''repair'',
    Msg_type: ''status'',
    Msg_text: ''OK''
  }
]



import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class RepairTable{
        public static void main(String[] args){
            String url = "jdbc:mysql://localhost:3306/TUTORIALS";
            String username = "root";
            String password = "password";
            try{
                Class.forName("com.mysql.cj.jdbc.Driver");
                Connection connection = DriverManager.getConnection(url, username, password);
                Statement statement = connection.createStatement();
                System.out.println("Connected successfully...!");

                //Repair tables...!
                String sql = "REPAIR TABLE customers";
                statement.executeUpdate(sql);
                System.out.println("Table repaired successfully...!");

                connection.close();
            }
            catch(Exception e){
                System.out.println(e);
            }
        }
}

Output

The output obtained is as shown below −


Connected successfully...!
Table repaired successfully...!



import mysql.connector
#establishing the connection
connection = mysql.connector.connect(
    host=''localhost'',
    user=''root'',
    password=''password'',
    database=''tut''
)
table_name = ''tutorials_tbl_temp''
#Creating a cursor object 
cursorObj = connection.cursor()
repair_table_query = f"REPAIR TABLE {table_name}"
cursorObj.execute(repair_table_query)
print(f"Table ''{table_name}'' is repaired successfully.")
# Fetch and consume any remaining results from the cursor
# ensuring that there are no unread results before closing the cursor.
for _ in cursorObj:
    pass
cursorObj.close()
connection.close()

Output

Following is the output of the above code −


Table ''tutorials_tbl_temp'' is repaired successfully.



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