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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").