MySQL Repair Table

Introduction to MySQL Repair Table

MySQL Repair Table is to repair the corrupted table. This repair table doesn’t work for all the storage engines. Normally we might never get to use the “Repair table”, but when a disaster occurs then we get the data back from the “MyISAM” table. We need a few privileges like SELECT and INSERT for the table. It works only for the “MyISAM” storage engine and not for the “InnoDB” storage engine. So we need to change the storage engine to “MyISAM”. It’s always a good measure to take the backup of the table before performing the “Repair Table” as it might cause loss of data. We have the options of Quick, Extended, and USE_FRM that are applicable and defined in the syntax level. In this session let us discuss the “Repairable” along with the example.

Syntax

Below is the syntax of MySQL Repair Table

REPAIR[NO_WRITE_TO_BINLOG|LOCAL] TABLEtable_name1[,table_name2]... [table_nameN] [QUICK][EXTENDED][USE_FRM]

How does MySQL Repair Table work?

Let us see how MySQL Repair Table

Code:

REPAIR[NO_WRITE_TO_BINLOG|LOCAL] TABLEtable_name1[,table_name2]... [table_nameN] [QUICK][EXTENDED][USE_FRM]

Here if we consider each option and its use:

NO_WRITE_TO_BINLOG | LOCAL: By default, the Binary log is the place where the server writes the “Repair Table” for the replication slaves. To suppress the logging, we specify the option “NO_WRITE_TO_BINLOG” or Local.

QUICK: If we specify the “QUICK” option, it means we are trying to repair only the “index” file and not the data file. It is basically done by myisamchk –recover –quick.

EXTENDED: It creates one index at a time with sorting instead of creating row by row. It can be done by myisamchk –safe –recover.

USE_FRM: If the.MYI index file is missing or if the header is corrupted. This option tells not to trust the.MYI information and re-create the information from the data dictionary. It can’t be done by myisamchk.

Now let us create the table and alter the storage engine and create a “repair table”.

Code:

CREATE TABLE LOAN_TABLE(
LOAN_NO VARCHAR(25)PRIMARY KEY,
NAME VARCHAR(25),
AMOUNT INTEGER(10),
AP_DATE DATE
);

Inserting data into the loan_table table:

Code:

INSERT INTO LOAN_TABLE VALUES ('3A341','Ram', 189000,'2018-09-08');
INSERT INTO LOAN_TABLE VALUES ('4E251',' Ravi', 125000,'2018-09-09');
INSERT INTO LOAN_TABLE VALUES ('1R121',' Santosh', 169000,'2018-09-10');
INSERT INTO LOAN_TABLE VALUES ('53RT1',' Samuel', 139560,'2018-09-11');
INSERT INTO LOAN_TABLE VALUES ('2RR31',' Kartika', 188756,'2018-09-12');
INSERT INTO LOAN_TABLE VALUES ('8PP91',' Donald', 122568,'2018-09-13');
INSERT INTO LOAN_TABLE VALUES ('0PK91',' Donald Parker', 135684,'2018-09-14');
INSERT INTO LOAN_TABLE VALUES ('7JI81',' Danny', 190000,'2018-09-15');
INSERT INTO LOAN_TABLE VALUES ('OWE31',' Harsh', 164988,'2018-09-16');
INSERT INTO LOAN_TABLE VALUES ('PPL11',' Blue park', 127568,'2018-09-17');
INSERT INTO LOAN_TABLE VALUES ('R34E1','chai', 156000,'2018-09-18');
INSERT INTO LOAN_TABLE VALUES ('WE451','Chang',179000,'2018-09-19');

Now let us select the table:

select * from LOAN_TABLE;

Output:

Here below query is used to check the storage engine for the specified table.

Code:

select table_name, engine from information_schema.tables where table_name='loan_table';

Output:

Here it is “InnoDB”. So when we create the repair table for this storage engine table it throws an error:

Code:

REPAIR TABLE LOAN_TABLE;

Output:

Alter the table storage engine to “MyISAM” and then try to create the “repair table”.

Code:

ALTER TABLE LOAN_TABLE ENGINE='MyISAM';
Now let us create the “repair table” for the loan_table;
REPAIR TABLE LOAN_TABLE;

Output:

Here from the output, we can see that it has four columns Table, Op, Msg_type, and Msg_text.

Examples to Implement MySQL Repair Table

Now let us create another table:

Example #1

Code:

create table Weather_temperature
(
Days date,
London Float (5,2),
New_York Float (5,2),
India Float (5,2),
America Float (5,2),
Africa Float (5,2),
China Float (5,2),
Australia Float (5,2)
)ENGINE=MyISAM;  /* -- Storage engine as “MyISAM” instead of default one “InnoDB” -*/

Now let us insert the data into the table as below:

Code:

insert into weather_temperature values ('2020-01-01', 36.7, 34.6, 39.1, 39.8, 34.1, 29.0, 37.7 );
insert into weather_temperature values ('2020-01-02', 31.7, 39.6, 31.1, 32.8, 40.0, 39.0, 34.7 );
insert into weather_temperature values ('2020-01-03', 32.7, 38.6, 38.1, 31.8, 45.2, 34.0, 32.7 );
insert into weather_temperature values ('2020-01-04', 33.7, 37.6, 32.1, 36.8, 49.1, 31.0, 37.7 );
insert into weather_temperature values ('2020-01-05', 34.7, 36.6, 37.1, 34.8, 49.7, 36.0, 39.7 );
insert into weather_temperature values ('2020-01-06', 35.7, 35.6, 33.1, 30.8, 49.2, 33.0, 31.7 );
insert into weather_temperature values ('2020-01-07', 36.7, 34.6, 34.1, 33.8, 48.9, 38.0, 39.7 );
insert into weather_temperature values ('2020-01-08', 37.7, 23.6, 35.1, 39.8, 45.5, 36.0, 33.7 );
insert into weather_temperature values ('2020-01-09', 28.7, 30.6, 36.1, 32.8, 49.9, 30.0, 37.7 );
insert into weather_temperature values ('2020-01-10', 30.7, 31.6, 29.1, 33.8, 50.0, 33.0, 31.7 );

Now let us select the table and see the output:

SELECT * FROM WEATHER_TEMPERATURE;

Output:

Example #2

Here we have created the table with the storage engine as “MyISAM”. So the repair table will be executed without any error:

Code:

REPAIR TABLE WEATHER_TEMPERATURE_DATA QUICK extended;

Output:

Conclusion

MySQL Repair Table is for the repairs of the corrupted table. This repair table doesn’t work for all the storage engines. It works only for the “MyISAM” storage engine and not for the “InnoDB” storage engine. So we need to change the storage engine to “MyISAM”. It’s always a good measure to take the backup of the table before performing the “Repair Table” as it might cause loss of data. We have the options of Quick, Extended, and USE_FRM that are applicable and defined in the syntax level.

Recommended Articles

This is a guide to MySQL Repair Table. Here we discuss an introduction to MySQL Repair Table, syntax, how does it work with query examples. You can also go through our other related articles to learn more –

1. MySQL Administration
2. MySQL Database Repair
3. MySQL Server
4. MySQL Timestamp