SQL · Theory

POSITION()()

Theory

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POSITION()()

POSITION() POSITION('a' IN name) — SQL form of locate. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = POSITION(col).

Board: SELECT POSITION('a' IN 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). IN is part of the syntax here.

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

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

Exam tip

Say what POSITION returns, then SELECT POSITION('a' IN name) FROM students;

POSITION()() — sample query

-- POSITION()()
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;

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

Short notes

DefPOSITION() POSITION('a' IN name) — SQL form of locate.
RuleSELECT POSITION('a' IN name) FROM students;
TrapIN is part of the syntax here.

SQL · Theory

POSITION()()

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Theory

158/439

POSITION()()

POSITION() POSITION('a' IN name) — SQL form of locate. You use it in SELECT (and sometimes WHERE/UPDATE). It does not change stored data unless you UPDATE … SET col = POSITION(col).

Board: SELECT POSITION('a' IN 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). IN is part of the syntax here.

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

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

Exam tip

Say what POSITION returns, then SELECT POSITION('a' IN name) FROM students;

POSITION()() — sample query

-- POSITION()()
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;

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

Short notes

DefPOSITION() POSITION('a' IN name) — SQL form of locate.
RuleSELECT POSITION('a' IN name) FROM students;
TrapIN is part of the syntax here.

POSITION()()

POSITION()() — sample query

Short notes

Questions

POSITION()()

POSITION()() — sample query

Short notes

Questions