MySQL supports three comment styles:
- From a ‘– ‘ to the end of the line. The double dash-comment style requires at least whitespace or control character (space, tab, newline, etc) after the second dash.
- From a ‘#' to the end of the line. SELECT.
- C-style comment /**/ can span multiple lines.
Keeping this in consideration, how do I comment in a MySQL query?
In MySQL, a comment started with — symbol is similar to a comment starting with # symbol. When using the — symbol, the comment must be at the end of a line in your SQL statement with a line break after it. This method of commenting can only span a single line within your SQL and must be at the end of the line.
Also Know, what does /* mean in SQL? /* means a start of a multiline comment. For example: /* CREATE PROC A_SAMPLE_PROC BEGIN AS SELECT * FROM A_SAMPLE_TABLE END */ while — means single line comment. Keyboard shortcut for commenting in MS SQL Server Studio is Ctrl + K, Ctrl + C.
Also question is, what is the comment character in SQL?
This method of commenting must be at the end of the line and be in a single line. A comment in SQL that starts with /* symbol and ends with */ and can span several lines within your SQL.
How do I edit a table in MySQL workbench?
You can add or modify the columns or indexes of a table, change the engine, add foreign keys, or alter the table name. To access the MySQL Table Editor, right-click a table name in the Navigator area of the sidebar with the Schemas secondary tab selected and click Alter Table.
What is the shortcut to comment out in SQL?
To comment out lines of code in SQL Server Management Studio (SSMS) Query Window, select lines of code you want to comment out and hit the keyboard shortcut ‘CTRL+K' followed by ‘CTRL+C'.
How do you comment on a database?
Comments Within SQL Statements
- Begin the comment with a slash and an asterisk (/*). Proceed with the text of the comment. This text can span multiple lines.
- Begin the comment with — (two hyphens). Proceed with the text of the comment. This text cannot extend to a new line.
Is MySQL case sensitive?
Database and table names are not case sensitive in Windows, and case sensitive in most varieties of Unix. In MySQL, databases correspond to directories within the data directory. Consequently, the case sensitivity of the underlying operating system plays a part in the case sensitivity of database and table names.
How do I concatenate in MySQL?
MySQL CONCAT() function is used to add two or more strings.
- There may be one or more arguments.
- Returns the string that results from concatenating the arguments.
- Returns a nonbinary string, if all arguments are nonbinary strings.
- Returns a binary string, if the arguments include any binary strings.
What is MySQL injection in php?
SQL injection refers to the act of someone inserting a MySQL statement to be run on your database without your knowledge. Injection usually occurs when you ask a user for input, like their name, and instead of a name they give you a MySQL statement that you will unknowingly run on your database.
What are MySQL data types?
MySQL supports SQL data types in several categories: numeric types, date and time types, string (character and byte) types, spatial types, and the JSON data type.
How do I comment in PostgreSQL?
In PostgreSQL, a comment started with — symbol is similar to a comment starting with # symbol. When using the — symbol, the comment must be at the end of a line in your SQL statement with a line break after it. This method of commenting can only span a single line within your SQL and must be at the end of the line.
How do I comment in Sqlyog?
Advanced Editing Features
- Make Selection Uppercase: To change selected text to uppercase (or press Ctrl+Shift+U)
- Make Selection Lowercase: To change selected text to lowercase (or press Ctrl+Shift+L)
- Comment Selection: To comment the selected text (or press Ctrl+Shift+C)
- Remove Comment From Selection: To remove the comment (or Ctrl+Shift+R).
What does count (*) do in SQL?
COUNT(*) returns the number of rows in a specified table, and it preserves duplicate rows. It counts each row separately. This includes rows that contain null values.
IS NOT NULL SQL?
The IS NOT NULL condition is used in SQL to test for a non–NULL value. It returns TRUE if a non–NULL value is found, otherwise it returns FALSE. It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.
What is SQL Select statement?
The SQL SELECT statement returns a result set of records from one or more tables. A SELECT statement retrieves zero or more rows from one or more database tables or database views. ORDER BY specifies an order in which to return the rows. AS provides an alias which can be used to temporarily rename tables or columns.
What does the symbol mean in SQL?
The @CustID means it's a parameter that you will supply a value for later in your code. The database engine puts the parameter value into where the placeholder is, and there is zero chance for SQL injection.
What is %s in SQL?
%s is a placeholder used in functions like sprintf. $sql = sprintf($sql, “Test”); This would replace %s with the string “Test”. It's also used to make sure that the parameter passed actually fits the placeholder. You might use %d as a placeholder for digits, but if sprintf would receive a string it would complain.
What does * symbol mean?
It almost always means “and,” both in and outside of mathematics. * This symbol is called an asterisk. In mathematics, we sometimes use it to mean multiplication, particularly with computers. For example, 5*3 = 5 times 3 = 15.
What does ## mean in SQL?
A single instance ( # ) refers to a temporary object that lives/dies with the current session while a double instance ( ## ) is a global object. https://stackoverflow.com/questions/3166117/what-does-the-sql-symbol-mean-and-how-is-it-used/3166148#3166148. Share a link to this answer.
IS NULL in SQL?
The SQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank. A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces.
What is the use of MySQL workbench?
MySQL Workbench is a unified visual tool for database architects, developers, and DBAs. MySQL Workbench provides data modeling, SQL development, and comprehensive administration tools for server configuration, user administration, backup, and much more. MySQL Workbench is available on Windows, Linux and Mac OS X.
How do I show tables in MySQL workbench?
Inside the workbench right click the table in question and click “Select Rows – Limit 1000.” It's the first option in the pop-up menu. To get the convenient list of tables on the left panel below each database you have to click the tiny icon on the top right of the left panel.