Lowercase and Trim a Name — String Functions in SQL

The problem

Brightlane's contact deduplication job normalizes customer names by converting to lowercase and removing leading and trailing spaces before comparison.

Write a query to return the cleaned version of the name ' Owen Marshall '.

Output:

A single row with one column, normalized_name, containing the lowercased and trimmed string.

Schema · ecommerce 5 tables

categories

id integer

name text

parent_id? integer

products

id integer

name text

category_id integer

price numeric

stock_qty integer

attributes? jsonb

order_items

id integer

order_id integer

product_id integer

quantity integer

unit_price numeric

customers

id integer

name text

email text

city? text

country text

created_at timestamptz

is_active boolean

orders

id integer

customer_id integer

ordered_at timestamptz

status text

total_amount numeric

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Worked solution Try it yourself first

Solution query

SELECT
  TRIM(LOWER('  Owen Marshall  ')) AS normalized_name

The shape

The two functions compose in one expression: LOWER(...) runs first against the padded literal and produces ' owen marshall ', then TRIM(...) runs against that intermediate value and produces 'owen marshall'. Nesting from the inside out lets one SELECT expression carry both normalization steps the deduplication job needs.

Clause by clause

SELECT TRIM(LOWER(' Owen Marshall ')) AS normalized_name runs the two transforms in order. The inner LOWER returns the casing-normalized form of the input, padding included; the outer TRIM then strips the leading and trailing spaces from that result. The alias normalized_name labels the final cleaned value.
There is no FROM because both functions operate on the literal embedded in the SELECT. Each function takes one input and returns one output, and the two outputs chain straight through.

Why this order and not `LOWER(TRIM(...))`

Both orderings produce the same result on this input, because lowercasing leaves spaces unchanged and trimming leaves casing unchanged. The two transforms commute here. They do not always: a transform that depends on the boundary character (a SUBSTRING keyed off the first non-space, for instance) would care about whether trimming happened first. When transforms genuinely commute, either nesting reads correctly; the habit of running case normalization inside and trimming outside is a convention worth keeping for consistency across the pipeline.

You practiced composing TRIM(LOWER(...)) — chain two single-row transforms so the inner result feeds the outer call in one expression.

Return the cleaned version of the name `' Owen Marshall '`

The shape

Clause by clause

Why this order and not `LOWER(TRIM(...))`

Reading explains SQL. Writing it, over and over with instant feedback, is what makes you fluent.

The shape

Clause by clause

Why this order and not LOWER(TRIM(...))

Reading explains SQL. Writing it, over and over with instant feedback, is what makes you fluent.

Why this order and not `LOWER(TRIM(...))`