What does the SQL SELECT * from tablename statement do?

Selecting All Columns To retrieve all columns from a table without listing each one explicitly, you can use the asterisk (*) wildcard: SELECT * FROM table_name; This retrieves every column defined in the table. Lees verder »

Bron: medium.com

What does the SQL statement SELECT count(*) from table_name do?

The COUNT function returns the number of rows for which the expression evaluates to a non-null value. ( * is a special expression that is not evaluated, it simply returns the number of rows.) Lees verder »

What does the SQL statement SELECT top 5 * from table_name do?

The SELECT TOP clause in SQL Server is used to limit the rows returned by a query. It allows users to retrieve a specified number or percentage of rows from the result set, which is particularly useful when working with large datasets or when only a sample of the data is needed. Lees verder »

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