Akina

SELECT *
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE TABLE_SCHEMA = DATABASE() /* либо 'database_name' */
  AND TABLE_NAME = 'table_name'

SELECT *
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = DATABASE()
  AND TABLE_NAME = 'table_name'

SELECT categories.id, 
       categories.slug,  
       ct_ru.title title_ru,  
       ct_en.title title_en,  
       ct_de.title title_de
FROM categories
LEFT JOIN category_translations ct_ru ON category_translations.category_id=categories.id 
                                     AND category_translations.locale = 'ru'
LEFT JOIN category_translations ct_en ON category_translations.category_id=categories.id 
                                     AND category_translations.locale = 'en'
LEFT JOIN category_translations ct_de ON category_translations.category_id=categories.id 
                                     AND category_translations.locale = 'de';

CREATE TRIGGER trigger_name
EVENT ACTION ON table_name
FOR EACH ROW
BEGIN
    SET @trigger_name_table_name = CONCAT('executed, ', 'column_value=', NEW.column);
-- trigger action
    SET @trigger_name_table_name = NULL;
END;

будет ли использоваться индекс в запросе вида WHERE `field1` LIKE '_aa_a_'?

SELECT p.name, p.id 
FROM products AS p
JOIN product_country AS cp ON cp.product_id = p.id 
WHERE cp.country_id IN (1,2)
GROUP BY 1, 2
HAVING COUNT(DISTINCT cp.country_id) = 2;

SELECT *
FROM tablename
ORDER BY client_id IS NULL, hub_id IS NULL
LIMIT 1

SELECT DISTINCT data.*
FROM data
JOIN ( 
    SELECT 2 value 
    UNION ALL 
    SELECT 5 
    UNION ALL 
    SELECT 7
    ) criteria ON JSON_CONTAINS(data.jsonarray, CAST(criteria.value AS JSON))

CREATE TABLE table_name (create_date DATE);

ALTER TABLE table_name 
PARTITION BY RANGE(create_date + 0) (
    PARTITION p_old VALUES LESS THAN(20111201),
    PARTITION p_1 VALUES LESS THAN(20120201),
    PARTITION p_2 VALUES LESS THAN(MAXVALUE)
);

ALTER TABLE table_name
    REORGANIZE PARTITION p_2 INTO (
        PARTITION p_2 VALUES LESS THAN (20130101),
        PARTITION p_max VALUES LESS THAN (MAXVALUE)
);

UPDATE table
SET {columns} = {values}
ORDER BY created_at ASC LIMIT 1;

create table if not exists dialogs (
    id int primary key auto_increment, 
    user_id_one int not null, 
    foreign key (user_id_one) references users (id), 
    user_id_two int not null, 
    foreign key (user_id_two) references users (id)
)