SLICE¶

The SLICE statement is a function in GlueSQL that allows you to retrieve a subsection of a list. It is analogous to slicing operations in many programming languages.

Syntax¶

SELECT SLICE(column_name, start_index, length) AS alias_name FROM table_name;

• column_name: Name of the column containing the list.
• start_index: The starting index from where the slice should begin. This value can be negative.
• length: The number of elements to be included in the slice.

Examples¶

Consider the following table Test:

CREATE TABLE Test (
    list LIST
);

With the following data:

INSERT INTO Test VALUES
('[1,2,3,4]');

1. Basic Slicing¶

Retrieve the first 2 elements from a list.

SELECT SLICE(list, 0, 2) AS value FROM Test;

Result:

[1, 2]

2. Slicing Beyond List Length¶

If the combined start index and length exceed the list size, SLICE will return all possible elements without error.

SELECT SLICE(list, 2, 5) AS value FROM Test;

Result:

[3, 4]

3. Start Index Beyond List Length¶

If the start index alone exceeds the list size, SLICE will return an empty list.

SELECT SLICE(list, 100, 5) AS value FROM Test;

Result:

[]

4. Using Negative Start Index¶

A negative start index counts from the end of the list.

SELECT SLICE(list, -1, 1) AS value FROM Test;

Result:

[4]

Another example of a negative start index.

SELECT SLICE(list, -2, 4) AS value FROM Test;

Result:

[3, 4]

If the absolute value of the negative start index exceeds the list length, it is treated as index 0.

SELECT SLICE(list, -234, 4) AS value FROM Test;

Result:

[1, 2, 3, 4]

Errors¶

• Using a non-list value for slicing will result in an error: ListTypeRequired.
• Using a non-integer value for the start index or length will result in an error: FunctionRequiresIntegerValue("SLICE").