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MySQLi Articles
Page 333 of 341
How to convert MyISAM to InnoDB storage engine in MySQL?
To convert the MyISAM Engine to InnoDB, we can use the ALTER command. Let us now create a table with the help of engine MyISAM. mysql> create table MyISAMToInnoDBDemo -> ( -> id int, -> Name varchar(100) -> )ENGINE=MyISAM; Query OK, 0 rows affected (0.19 sec) To check if the table is created with engine MyISAM or not. mysql> SELECT TABLE_NAME, ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = 'business' and ENGINE = 'MyISAM'; The following is the output that displays the table created with MyISAM ...
Read MoreHow to debug Lock wait timeout exceeded on MySQL?
The debug Lock wait timeout situation occurs because of some threads. If one thread is holding on to some records for a very long time, it means the thread has exceeded time. To see all the details, implement the following query − mysql> SHOW ENGINE INNODB STATUS; The following is the output. +--------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Type | Name | Status ...
Read MoreWhy doesn't MySQL support millisecond / microsecond precision?
The millisecond/ microsecond precision wasn’t supported in previous versions like 5.6.4. But now MySQL supports millisecond/ microsecond precision with timestamp, datetime, and time. The official statement. “MySQL now supports fractional seconds for TIME, DATETIME, and TIMESTAMP values, with up to microsecond precision”. You can check the MySQL version on your system using the version() method. mysql> SELECT version(); The following is the output. +-----------+ | version() | +-----------+ | 8.0.12 | +-----------+ 1 row in set (0.01 sec) Let us now see the syntax to check the date difference. mysql> SELECT DATEDIFF(now(), ...
Read MoreHow do I kill all the processes in MySQL “show processlist”?
We can kill the processes with the help of the ‘kill’ command. However, you need to kill those processes one by one, since MySQL does not have any massive kill command. To check how many processes exist, use ‘show processlist’ mysql> show processlist; The following is the output. +----+-----------------+-----------------+------+---------+------+------------------------+------------------+ | Id | User | Host | db | Command | Time | State ...
Read MoreHow to save MySQL query output to excel or .txt file?
To save MySQL query output into a text file, we can use the OUTFILE command. Let us first create a table. mysql> create table SaveintoTextFile -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.55 sec) Inserting records into the table. mysql> insert into SaveintoTextFile values(1, 'John'); Query OK, 1 row affected (0.44 sec) mysql> insert into SaveintoTextFile values(101, 'Carol'); Query OK, 1 row affected (0.17 sec) mysql> insert into SaveintoTextFile values(3, 'David'); Query OK, 1 row ...
Read MoreHow to display current connection info in MySQL?
MySQL provides many functions that give the current connection information. For instance, to know about the current user, use the user() function. Syntax mysql> SELECT CURRENT_USER(); Here is the output that displays the name of the current user. +----------------+ | CURRENT_USER() | +----------------+ | root@% | +----------------+ 1 row in set (0.00 sec) In the above, % tells us about localhost. To check the current connection id, use the following method − mysql> SELECT CONNECTION_ID(); The following is the output that shows the current connection id. ...
Read MoreHow to create boolean column in MySQL with false as default value?
To create a column with ‘false’ as the default value, we can use the concept of “default” at the time of creation of the table. Note − 0 represents false and 1 represents true. Creating a table using “default” false. mysql> create table TrueFalseTable -> ( -> Adult boolean default false -> ); Query OK, 0 rows affected (0.65 sec) Inserting records with no value, since we have set “default” above. mysql> insert into TrueFalseTable values(); Query OK, 1 row affected (0.16 sec) To display records. ...
Read MoreHow to use union and order by clause in MySQL?
Union is a type of operator in MySQL. We can use ORDER BY with this to filter records. Use UNION if you want to select rows one after the other from several tables or several sets of rows from a single table all as a single result set. Let us see an example. Creating first table mysql> create table UnionDemo1 -> ( -> id int -> ); Query OK, 0 rows affected (0.59 sec) Inserting records into first table. mysql> insert into UnionDemo1 values(1), (4), (10); Query OK, ...
Read MoreHow to get a list of MySQL views?
To get a list of MySQL views, we can use the SELECT command with LIKE operator. Let us see the syntax first. mysql> SELECT TABLE_SCHEMA, TABLE_NAME -> FROM information_schema.tables -> WHERE TABLE_TYPE LIKE 'VIEW'; The following is the output that displays the total number of views. +--------------+-----------------------------------------------+ | TABLE_SCHEMA | TABLE_NAME | +--------------+-----------------------------------------------+ | sys ...
Read MoreHow to repair MySQL tables from the command line?
The repair of MySQL tables is only applicable to MyISAM engine type, not for InnoDB. Therefore, we need to change the Engine type to MyISAM. The following is an example. Creating a table mysql> create table RepairTableDemo -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.51 sec) To convert this table to engine type MyISAM, use ALTER. mysql> ALTER TABLE RepairTableDemo ENGINE = MyISAM; Query OK, 0 rows affected (1.14 sec) Records: 0 Duplicates: 0 Warnings: ...
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