........... symbol is used to see every column of a table.

Question

Accepted Answer

The correct option is (2):
The asterisk symbol (\*) is the standard and most widely used wildcard in Structured Query Language (SQL) to represent "all columns" or "all fields" within a specified table. When you write a query like `SELECT * FROM students;`, the asterisk instructs the database management system to retrieve data from every single column defined in the `students` table. This is a fundamental command in database querying, allowing you to instantly view the entire schema and content of a table without having to type out each column name manually. It saves time and ensures no column is inadvertently omitted from the result set.

The incorrect option is (1):
The forward slash (/) is not a standard SQL symbol for selecting all columns. In most programming and database contexts, the forward slash is primarily recognized as the arithmetic operator for division. If you were to use it in a `SELECT` statement in place of the asterisk (e.g., `SELECT / FROM table`), the SQL parser would typically interpret it as an incorrect or incomplete arithmetic expression, resulting in a syntax error rather than retrieving the table data.

The incorrect option is (3):
The exclamation mark (\!) is generally not used in standard SQL for column selection. In many computing languages, the exclamation mark is associated with the logical NOT operator, used to negate a condition. For instance, in some SQL dialects, it can be used in combination with an equals sign as `!=` to mean "not equal to." However, using `!` by itself in the column list of a `SELECT` statement does not signify all columns and would be flagged by the database system as an invalid token or expression.

The incorrect option is (4):
The double hyphen (--) is the universally accepted symbol in SQL to denote a single-line comment. Any character or text that follows the `--` on the same line is entirely ignored by the SQL execution engine. Programmers use this symbol to add explanatory notes to their code, ensuring that the notes do not interfere with the actual commands. Since the primary function of `--` is to prevent code from running, it cannot be an operator used to actively select and display data like all columns of a table.