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Filter Function

The filter function in SwartzDB allows selecting, transforming, and formatting specific fields from a dataset while applying operations like concatenation, case conversion, and arithmetic calculations.

How filter Works​

Basic Field Selection​

You can extract specific fields from an array:

$filteredData = $sdb->filter($data, ["name", "age"]);

This returns an array containing only the name and age columns.

Applying Operations​

Concatenation (concat)​

You can merge multiple columns into one:

$filteredData = $sdb->filter($data, [
    "full_name" => ["concat" => ["first_name", "s:: ", "last_name"]]
]);
  • This merges first_name and last_name with a space in between.
  • "s:: " is a static value, meaning it's not a column but a fixed space character.

Changing Case (uppercase, lowercase)​

You can convert text to uppercase or lowercase:

$filteredData = $sdb->filter($data, [
    "upper_name" => ["uppercase" => "name"],
    "lower_email" => ["lowercase" => "email"]
]);
  • "uppercase" => "name" changes name to uppercase.
  • "lowercase" => "email" changes email to lowercase.

Performing Arithmetic (sum, difference)​

You can perform calculations on numerical columns:

$filteredData = $sdb->filter($data, [
    "total_price" => ["sum" => ["price", "tax"]],
    "profit" => ["difference" => ["revenue", "cost"]]
]);
  • "sum" => ["price", "tax"] adds price and tax.
  • "difference" => ["revenue", "cost"] subtracts cost from revenue.

Formatting Dates (date_format)​

You can convert dates into a different format:

$filteredData = $sdb->filter($data, [
    "formatted_date" => ["date_format" => ["date_column", "d M Y"]]
]);
  • "date_format" => ["date_column", "d M Y"] converts date_column into "05 Mar 2024" format.

Understanding Static Values (s::)​

Any argument in filter is treated as a column or an operation unless it starts with s::.
If an argument starts with "s::", it is a static value (a fixed value, not a column name).

Example:​

$filteredData = $sdb->filter($data, [
    "greeting" => ["concat" => ["s::Hello, ", "name"]]
]);
  • "s::Hello, " is a static string.
  • "name" is a column.

Example with Numbers​

$filteredData = $sdb->filter($data, [
    "taxed_price" => ["sum" => ["price", "s::5"]]
]);
  • "price" is a column.
  • "s::5" is a fixed value (adding 5 to the price).

When to Use Filtering?​

✅ Use filter when:

  • You need to extract specific columns from a dataset.
  • You want to format or transform values before use.
  • You need computed fields (concatenations, calculations, case changes).
  • You need to format dates consistently.

❌ Do NOT use filter when:

  • You need to delete rows (use remove_row instead).
  • You want to update records (use update_row instead).

Conclusion​

Filtering in SwartzDB is powerful and flexible, allowing you to extract, modify, and compute data dynamically. Static values (s::) help mix constants with column data, making operations more versatile.