SQL · Theory

Trim()()

Theory

172/439

Trim()()

TRIM() drops spaces from both ends. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = TRIM(col).

Board: SELECT TRIM(name) FROM students; Run it. Say the result out loud. If the column is NULL, the result is often NULL — wrap with IFNULL if you need a blank instead.

String indexes in MySQL start at 1, not 0 (SUBSTR, INSTR, LEFT). Does not remove spaces in the middle.

Interview — name TRIM, one argument list, one example on the students table. Don’t recite every string function.

On the example next to this theory: Trim()(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Exam tip

Say what TRIM returns, then SELECT TRIM(name) FROM students;

Trim()() — sample query

-- Trim()()
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

Trim()(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefTRIM() drops spaces from both ends.
RuleSELECT TRIM(name) FROM students;
TrapDoes not remove spaces in the middle.

SQL · Theory

Trim()()

← All stacks

Theory

172/439

Trim()()

TRIM() drops spaces from both ends. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = TRIM(col).

Board: SELECT TRIM(name) FROM students; Run it. Say the result out loud. If the column is NULL, the result is often NULL — wrap with IFNULL if you need a blank instead.

String indexes in MySQL start at 1, not 0 (SUBSTR, INSTR, LEFT). Does not remove spaces in the middle.

Interview — name TRIM, one argument list, one example on the students table. Don’t recite every string function.

On the example next to this theory: Trim()(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Exam tip

Say what TRIM returns, then SELECT TRIM(name) FROM students;

Trim()() — sample query

-- Trim()()
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

Trim()(): create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefTRIM() drops spaces from both ends.
RuleSELECT TRIM(name) FROM students;
TrapDoes not remove spaces in the middle.

Trim()()

Trim()() — sample query

Short notes

Questions

Trim()()

Trim()() — sample query

Short notes

Questions