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Articles on Trending Technologies
Technical articles with clear explanations and examples
Alter a MySQL column to be AUTO_INCREMENT?
Let’s say we have a table and now there is a requirement to add AUTO_INCREMENT on column name. For that, use the MODIFY command. Here, we will create a demo table first. mysql> create table AddingAutoIncrement -> ( -> Id int, -> Name varchar(200), -> Primary key(Id) -> ); Query OK, 0 rows affected (0.47 sec) We have created a table above and now let us alter the table to add AUTO_INCREMENT on column name ‘Id’. The syntax is as follows − ...
Read MoreWhat does the KEY keyword mean in MySQL?
Key is synonymous to an index. If you want to create an index for a column, then use ‘Key’. As stated in the official docs: KEY is normally a synonym for INDEX. The key attribute PRIMARY KEY can also be specified as just KEY when given in a column definition. This was implemented for compatibility with other database systems. The key can be used with Primary Key: Let us first create a table. Here is the query to set primary key for a column “id”. mysql> create table KeyDemo -> ( ...
Read MoreWhen to use MyISAM and InnoDB?
InnoDB is a general-purpose storage engine that balances high reliability and performance. Since MySQL 5.6, InnoDB is the default MySQL storage engine. InnoDB can be used for various purposes. Here are some of them − It can be used for transaction purpose i.e. all ACID properties. InnoDB can be used for row level locking, that means it gives higher performance as compared to MyISAM. InnoDB can be used for both data and index for a large buffer pool. InnoDB can be used when we need better performance than MyISAM. MyISAM is the default storage engine for the MySQL ...
Read MoreHow can I return 0 for NULL in MySQL?
We can return 0 for NULL in MySQL with the help of IFNULL() method. The syntax of IFNULL() is as follows. IFNULL(YOUREXPRESSION, 0); Let us see an example. First, we will create a table. mysql> create table NullDemoWithZero -> ( -> id varchar(200) -> ); Query OK, 0 rows affected (0.65 sec) After creating a table, let us insert some records in the table using the INSERT command. The query is as follows − mysql> insert into NullDemoWithZero values(); Query OK, 1 row affected (0.16 sec) ...
Read MoreHow to escape apostrophe (') in MySQL?
We can escape apostrophe (‘) in MySQL in the following two ways − We can use backslash. We can use single quotes twice (double quoted) Using backslash Let us first create a table. mysql> create table SingleQuotesDemo - > ( - > id int, - > name varchar(100) - > ); Query OK, 0 rows affected (1.16 sec) Following direct usage does not give the desired result for name “John’s”. mysql> insert into SingleQuotesDemo values(1, 'John's'); '> Let us now use backslash. ...
Read MoreHow to get a list of MySQL user accounts?
To get the list of MySQL user accounts, we can use “SELECT USER”. The following is the query to display the list. SELECT User FROM mysql.user; Here is the output. +------------------+ | User | +------------------+ | John | | Mac | | Manish | | mysql.infoschema | | mysql.session ...
Read MoreIs it possible to have a function-based index in MySQL?
Function-based index wasn’t possible in MySQL versions below 5.6. Firstly, to create function-based index in MySQL, we will create a table. mysql> create table FunctionIndexDemo - > ( - > FirstName varchar(100) - > ); Query OK, 0 rows affected (0.70 sec) Let us see the syntax to create a function based index. create index index_name on yourTableName (column_name(IntegerSize)); Here is the query. mysql> create index indFirstName on FunctionIndexDemo (FirstName(6)); Query OK, 0 rows affected (0.56 sec) Records: 0 Duplicates: 0 Warnings: 0 ...
Read MoreMySQL's DESCRIBE command?
The MySQL’s DESCRIBE or DESC both are equivalent. The DESC is the short form of DESCRIBE command and used to dipslay the information about a table like column names and constraints on column name. The DESCRIBE command is equivalent to the following command − SHOW columns from yourTableName command. The following is the query that display information about a table with the help of DESCRIBE command. The query is as follows. mysql> DESCRIBE Student; Above, Student is the table name in my database. The above query generates the following output. +-------+--------------+------+-----+---------+-------+ | Field | Type ...
Read MoreHow to disable ONLY_FULL_GROUP_BY in MySQL?
You can enable ONLY_FULL_GROUP_BY in MySQL as shown in the following query − mysql> SET sql_mode = 'ONLY_FULL_GROUP_BY'; Query OK, 0 rows affected (0.01 sec) As shown above, we can enable ONLY_FULL_GROUP_BY with the help of SET command. To disable ONLY_FULL_GROUP_BY with the help of the following query − mysql> SET GLOBAL sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY','')); Query OK, 0 rows affected (0.04 sec) We have disabled ONLY_FULL_GROUP_BY successfully.
Read MoreHow to create a MySQL table with MyISAM engine table?
To create a MySQL table with MyISAM engine, we can use ENGINE command. Let us first create a table using CREATE command. mysql> create table StudentRecordWithMyISAM -> ( -> Id int, -> StudentName varchar(100), -> StudentAge int -> )ENGINE=MyISAM; Query OK, 0 rows affected (0.26 sec) Above, we have set the ENGINE as “MyISAM”. To check how many columns are present in the table, use DESC command. mysql> DESC StudentRecordWithMyISAM; The following is the output. +-------------+--------------+------+-----+---------+-------+ | Field ...
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