What are the MySQL commands?

What are the MySQL commands?

• mysql — The MySQL Command-Line Client.
• mysqladmin — A MySQL Server Administration Program.
• mysqlcheck — A Table Maintenance Program.
• mysqldump — A Database Backup Program.
• mysqlimport — A Data Import Program.
• mysqlpump — A Database Backup Program.
• mysqlshow — Display Database, Table, and Column Information.

What is MySQL example?

An Example for the Beginners (But NOT for the dummies) A MySQL database server contains many databases (or schemas). Each database consists of one or more tables. A table is made up of columns (or fields) and rows (records).

What is query in MySQL?

In relational database management systems, a query is any command used to retrieve data from a table. In Structured Query Language (SQL), queries are almost always made using the SELECT statement. MySQL is an open-source relational database management system.

How do I use MySQL?

To create a MySQL database and user, follow these steps:

1. At the command line, log in to MySQL as the root user: mysql -u root -p.
2. Type the MySQL root password, and then press Enter.
3. Type \q to exit the mysql program.
4. To log in to MySQL as the user you just created, type the following command.

What is join in MySQL?

Description. MySQL JOINS are used to retrieve data from multiple tables. A MySQL JOIN is performed whenever two or more tables are joined in a SQL statement. There are different types of MySQL joins: MySQL INNER JOIN (or sometimes called simple join)

What is %s in MySQL?

It is a formatted string where %s is a placeholder. I suspect that $sql is handed to sprintf to transform it into a real query. Example: $name = ‘posts’; $sql = “SELECT * FROM page_table WHERE page_name = ‘%s’ LIMIT 1”; $formattedSql = sprintf($sql, $name);

How do I insert a quote in MySQL?

1. Click the Windows “Start” button and select “All Programs.” Click “MySQL,” then click “Query Browser” to open the MySQL programming application.
2. Log in to the MySQL server using your username and password.
3. Type the MySQL insert statement that inserts the characters, placing a backslash in front of any commas or quotes.

How do I escape MySQL?

MySQL QUOTE() produces a string which is a properly escaped data value in an SQL statement, out of a user supplied by the string as an argument. The function achieves this by enclosing the string with single quotes, and by preceding each single quote, backslash, ASCII NUL and control-Z with a backslash.

Does varchar allow special characters MySQL?

It can hold numbers, letters and special characters. Microsoft SQL Server 2008 (and above) can store up to 8000 characters as the maximum length of the string using varchar data type.

What is varchar in MySQL?

Varchar in MySQL is a data type used for storing text whose length can have a maximum of 65535 characters. The maximum length of a VARCHAR in MySQL is subject to the maximum row size of 65,535 bytes, which is shared among all columns except TEXT/BLOB columns and the character set used.

What does varchar 20 mean?

The data type of varchar is Variable-length with non-Unicode character data. The storage size is the actual length of data entered + 2 bytes. • For varchar (20): The max storage size is: 20*1 byte +2 bytes=22 bytes;

Which modifier is used to automatically generate a number in MySQL?

AUTO_INCREMENT modifier

What is Auto_increment in MySQL?

Description. In MySQL, you can create a column that contains a sequence of numbers (1, 2, 3, and so on) by using the AUTO_INCREMENT attribute. The AUTO_INCREMENT attribute is used when you need to create a unique number to act as a primary key in a table.

What is self join?

A self JOIN is a regular join, but the table is joined with itself – this is extremely useful for comparisons within a table. Joining a table with itself means that each row of the table is combined with itself and with every other row of the table.

What is primary key SQL?

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

How do you create a primary key?

To select more than one field to create a composite key, hold down CTRL and then click the row selector for each field. On the Design tab, in the Tools group, click Primary Key. A key indicator is added to the left of the field or fields that you specify as the primary key.

What is primary key in DBMS with example?

A primary key is a column — or a group of columns — in a table that uniquely identifies the rows in that table. For example, in the table below, CustomerNo, which displays the ID number assigned to different customers, is the primary key. CUSTOMERS.

What is primary key give an example?

A primary key is either an existing table column or a column that is specifically generated by the database according to a defined sequence. For example, students are routinely assigned unique identification (ID) numbers, and all adults receive government-assigned and uniquely-identifiable Social Security numbers.

What are the types of keys in DBMS?

Summary. Seven Types of DBMS keys are Super, Primary, Candidate, Alternate, Foreign, Compound, Composite, and Surrogate Key. A super key is a group of single or multiple keys which identifies rows in a table.

What is unique key in DBMS with example?

The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint.

What is unique MySQL?

A unique key in MySQL is a single field or combination of fields that ensure all values going to store into the column will be unique. It means a column cannot stores duplicate values. It can accept a null value, but MySQL allowed only one null value per column.

What is the use of unique key?

The purpose of unique key is to enforce unique data. It is SQL constraint which allows you to uniquely identify each record or row in the database table. It is SQL constraint that doesnot allow the same value tobe assigned to two isolatedRecords in a database table. In the primary key, duplicate keys are not allowed.

How do you identify a super key?

The superkey is also known as superset key. If attribute set K is a superkey of relation R, then at all times it is the case that the projection of R over K has the same cardinality as R itself. A superkey is a set of attributes within a table whose values can be used to uniquely identify a tuple.