SQL · Theory

REPEAT()()

Theory

160/439

REPEAT()()

REPEAT() repeats text n times. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = REPEAT(col).

Board: SELECT REPEAT('*', 5); 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). Huge n can make a giant string.

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

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

Exam tip

Say what REPEAT returns, then SELECT REPEAT('*', 5);

REPEAT()() — sample query

-- REPEAT()()
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;

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

Short notes

DefREPEAT() repeats text n times.
RuleSELECT REPEAT('*', 5);
TrapHuge n can make a giant string.

SQL · Theory

REPEAT()()

← All stacks

Theory

160/439

REPEAT()()

REPEAT() repeats text n times. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = REPEAT(col).

Board: SELECT REPEAT('*', 5); 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). Huge n can make a giant string.

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

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

Exam tip

Say what REPEAT returns, then SELECT REPEAT('*', 5);

REPEAT()() — sample query

-- REPEAT()()
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;

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

Short notes

DefREPEAT() repeats text n times.
RuleSELECT REPEAT('*', 5);
TrapHuge n can make a giant string.

REPEAT()()

REPEAT()() — sample query

Short notes

Questions

REPEAT()()

REPEAT()() — sample query

Short notes

Questions