Final answer:
The MIN function is used in SQL to find the smallest value in a set. DISTINCT can be used with MIN to consider unique values once whereas ALL, being the default behavior, does not normally need to be explicitly stated.
Step-by-step explanation:
The MIN function is commonly used in SQL (Structured Query Language) to find the minimum value in a set of values. However, when it comes to using it with DISTINCT or ALL keywords, there's a specific context that needs to be understood. Normally, MIN is used without specifying either DISTINCT or ALL, as it implicitly operates on all values. However, if you want to consider each unique value just once when calculating the minimum, you would use DISTINCT with MIN. In contrast, ALL is the default behavior and does not need to be explicitly stated.
For instance, if you have a table with a column containing values 1, 1, 3, and 4, using MIN(DISTINCT column_name) would return the minimum unique value, which is 1, just like simply using MIN(column_name) because 1 is the lowest value in this set. Including ALL explicitly does not change the outcome; it's more of a semantic tool that clarifies your intention to include all values, including duplicates, in the operation, which is already the default behavior of MIN.