BEGIN;

CREATE TABLE examples (
--  name type      constraints
    id   BIGSERIAL PRIMARY KEY
);

CREATE TABLE example_texts (
--  name        type      constraints
    id          BIGSERIAL PRIMARY KEY,
    example_id  BIGINT    NOT NULL REFERENCES examples (id),
    language_id BIGINT    NOT NULL REFERENCES languages (id),
    index       BIGINT    NOT NULL,
    value       TEXT      NOT NULL,

--  CONSTRAINT name                  CHECK (condition)
    CONSTRAINT index_is_not_negative CHECK (index >= 0),
    CONSTRAINT value_is_sane_text    CHECK (is_sane_text(value))
);

CREATE UNIQUE INDEX example_texts_example_language_index
    ON example_texts (example_id, language_id, index);

COMMIT;