What does * represent in sql

The * symbol in SQL is a wildcard character, which means it can match any character sequence. Common uses include: Select all columns: SELECT * FROM table_name; Select a specific column range: SELECT * FROM table_name WHERE column_name BETWEEN start_value AND end_value ;Join table: SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;Search mode: SELECT * FROM table

SQL Medium The * symbol

In SQL query statements, the symbol represents a wildcard character, which can match any character sequence. This enables the notation to be used for a wide range of query operations.

Usage

• symbol has the following common uses:
• Select all columns: SELECT * FROM table_name;

This will select all columns of all records in the table.

• Select a specific column range: SELECT * FROM table_name WHERE column_name BETWEEN start_value AND end_value;

This will select the table All records within a specific column value range.

• Join table: SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;

This Two tables will be joined, using the specified join conditions.

• Search mode: When used with the LIKE operator, the * symbol can represent any number of characters. For example: SELECT * FROM table_name WHERE column_name LIKE '%pattern%';

This will select all records in column_name that contain the pattern character sequence.

• Aggregation functions:
• notation can be used with aggregate functions such as SUM() and COUNT():

<code>SELECT SUM(*) FROM table_name;</code>

This will calculate the sum of the specified column across all records in the table.

Other Notes

• • symbols cannot match line breaks.
• In some cases, you can use the % symbol as a wildcard character, which behaves similarly to the * symbol.
• In regular expressions, the * symbol has a different meaning and means repeating the previous element zero or more times.

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