SQL · Theory

Wildcards

Theory

305/439

Wildcards

LIKE wildcards — % any string, _ one character. Not * . In REGEXP, . and .* are different. Don’t mix the two languages.

ESCAPE if you need a literal % — LIKE '%10\%%' ESCAPE '\\' (messy — mention you can escape).

Trap — * from globbing files.

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

Exam tip

LIKE 'A%' and LIKE 'A_ha'. Not *.

Wildcards — sample query

-- Wildcards
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;

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

Short notes

DefLIKE % and _ . REGEXP is separate.
Rule% = many, _ = one.
TrapUsing * in LIKE.

SQL · Theory

Wildcards

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Theory

305/439

Wildcards

LIKE wildcards — % any string, _ one character. Not * . In REGEXP, . and .* are different. Don’t mix the two languages.

ESCAPE if you need a literal % — LIKE '%10\%%' ESCAPE '\\' (messy — mention you can escape).

Trap — * from globbing files.

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

Exam tip

LIKE 'A%' and LIKE 'A_ha'. Not *.

Wildcards — sample query

-- Wildcards
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;

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

Short notes

DefLIKE % and _ . REGEXP is separate.
Rule% = many, _ = one.
TrapUsing * in LIKE.

Wildcards

Wildcards — sample query

Short notes

Questions

Wildcards

Wildcards — sample query

Short notes

Questions