SQL · Theory

LOWER()()

Theory

150/439

LOWER()()

LOWER() lowercase. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = LOWER(col).

Board: SELECT LOWER(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 UPDATE the table by itself.

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

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

Exam tip

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

LOWER()() — sample query

-- LOWER()()
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;

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

Short notes

DefLOWER() lowercase.
RuleSELECT LOWER(name) FROM students;
TrapDoes not UPDATE the table by itself.

SQL · Theory

LOWER()()

← All stacks

Theory

150/439

LOWER()()

LOWER() lowercase. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = LOWER(col).

Board: SELECT LOWER(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 UPDATE the table by itself.

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

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

Exam tip

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

LOWER()() — sample query

-- LOWER()()
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;

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

Short notes

DefLOWER() lowercase.
RuleSELECT LOWER(name) FROM students;
TrapDoes not UPDATE the table by itself.

LOWER()()

LOWER()() — sample query

Short notes

Questions

LOWER()()

LOWER()() — sample query

Short notes

Questions