static addSale(products){

        //WHERE (SELECT stock FROM prais_informations WHERE code = ) > 20;
        let quer = 'INSERT INTO `sales` (`id`, `code`, `quantity`, `price`, `sum`, `idCheck`) VALUES ?;';            

        return new Promise((resolve, reject) => {
           
        pool.getConnection((err, connection) => {
            if (err)reject(err);
            
            connection.query(quer, [products.map(item => [null, item.id, item.quantity, item.price, item.sum, 3])], (err, rows) => {
                 if (err) {
                    reject(err);
                }

                resolve(rows);
                connection.release();
            });
        });
     });
    }

INSERT INTO `sales` (`id`, `code`, `quantity`, `price`, `sum`, `idCheck`) VALUES ? WHERE (SELECT stock FROM prais_informations WHERE code = ? ) >= ?; 

insert into orders (product_id, qty)
select 2, 20
where (SELECT qty_on_hand FROM products WHERE id = 2) > 20;

INSERT into orders (product_id, qty)
VALUES (2, 10, 100), ..., (id, qty, price)
WHERE (SELECT qty_on_hand FROM products WHERE id = 2) > 20 
AND (SELECT qty_on_hand FROM products WHERE id = 3) > 30 
AND (SELECT qty_on_hand FROM products WHERE id = 4) > 40;

// insert statment
let stmt = `INSERT INTO sales(`id`, `code`, `quantity`, `price`, `sum`, `idCheck`)  VALUES ?  `;

let todos = [
  [null, id, quantity, price, sum],
  [null, id1, quantity1, price1, sum1],
  [null, id2, quantity2, price2, sum2],
];

// execute the insert statment
connection.query(stmt, [todos], (err, results, fields) => {
  if (err) {
    return console.error(err.message);
  }
  // get inserted rows
  console.log('Row inserted:' + results.affectedRows);
});

1
INSERT INTO `sales` (`id`, `code`, `quantity`, `price`, `sum`, `idCheck`)
VALUES
(null, item.id, item.quantity, item.price, item.sum, 3),
(null, item.id, item.quantity, item.price, item.sum, 3)
, ... ,
(null, item.id, item.quantity, item.price, item.sum, 3);

SELECT true WHERE (SELECT prais_informations.stock FROM prais_informations WHERE prais_informations.code = 1 LIMIT 1) > 7 
UNION
SELECT true WHERE (SELECT prais_informations.stock FROM prais_informations WHERE prais_informations.code = 2 LIMIT 1) > 3

sales:  [
  { id: 2, quantity: 5, price: 123, sum: 615 },
  { id: 1, quantity: 9, price: 97, sum: 873 }
]

CREATE TABLE `sales` (
  `id` int UNSIGNED NOT NULL,
  `code` int UNSIGNED NOT NULL,
  `quantity` mediumint UNSIGNED NOT NULL,
  `price` decimal(7,2) NOT NULL,
  `sum` decimal(8,2) NOT NULL,
  `idCheck` int UNSIGNED NOT NULL,
  `data` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `prais_informations` (
  `id` mediumint UNSIGNED NOT NULL,
  `code` mediumint UNSIGNED NOT NULL,
  `stock` mediumint UNSIGNED NOT NULL,
  `price` decimal(7,2) NOT NULL,
  `trade_price` decimal(7,2) NOT NULL,
  `group_in_tree` smallint UNSIGNED NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

sales:  [
  { id: 2, quantity: 5, price: 123, sum: 615 },
  { id: 1, quantity: 9, price: 97, sum: 873 }
]

[
  { "code": 2, "quantity": 5, "price": 123, "sum": 615 },
  { "code": 1, "quantity": 9, "price": 97, "sum": 873 }
]

You can use a CASE statement to handle multiple if/then scenarios:

UPDATE table_to_update 
SET  cod_user= CASE WHEN user_rol = 'student' THEN '622057'
                   WHEN user_rol = 'assistant' THEN '2913659'
                   WHEN user_rol = 'admin' THEN '6160230'
               END
    ,date = '12082014'
WHERE user_rol IN ('student','assistant','admin')
  AND cod_office = '17389551';

BEGIN

DECLARE res INT;
DECLARE last_index INT;
SET @input := 'sales:  [  { id: 2, quantity: 5, price: 123, sum: 615 },  { id: 1, quantity: 9, price: 97, sum: 873 } ]';

SET @input:=REPLACE(@input, ' ', '');
SET @input:=REPLACE(@input, 'sales:', '');
SET @input:=REGEXP_REPLACE(@input, '([{,])([a-z])', '$1"$2');
SET @input:=REGEXP_REPLACE(@input, '([a-z]):', '$1":');

CREATE TEMPORARY TABLE new_tbl SELECT jtin.id AS jtin_id, jtin.quantity AS jtin_qty, pi.stock AS pi_qty, pi.price AS pi_price
FROM JSON_TABLE(@input,
                "$[*]"
                COLUMNS (id INT PATH "$.id" ,
                         quantity MEDIUMINT PATH "$.quantity",
                         price DECIMAL(7,2) PATH "$.price",
                         `sum` DECIMAL(8,2) PATH "$.sum"
                         )) AS jtin 
                LEFT JOIN prais_informations AS pi ON jtin.id  = pi.code;

SET res = (SELECT count(*) FROM new_tbl WHERE jtin_qty > pi_qty);

IF res = 0 THEN 
/*
  Инсертим новую запись, получившийся id, будет являтся id чека
*/
INSERT INTO checks(`data`, `user`) VALUES ( UNIX_TIMESTAMP(), 0);
SET last_index = (SELECT max(id) FROM checks);
/*
  Инсертим содержимое массива заказа в таблицу регистрации
*/
INSERT INTO sales(`code`, `quantity`, `price`, `sum`, `idCheck`) SELECT nt.jtin_id, nt.jtin_qty, nt.pi_price, (nt.jtin_qty * nt.pi_price), last_index FROM new_tbl AS nt;

/*
  Обновляем остатки на складе
*/

END IF

END

CREATE TABLE `sales` (
  `id` int UNSIGNED NOT NULL,
  `code` int UNSIGNED NOT NULL,
  `quantity` mediumint UNSIGNED NOT NULL,
  `price` decimal(7,2) NOT NULL,
  `sum` decimal(8,2) NOT NULL,
  `idCheck` int UNSIGNED NOT NULL,
  `data` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


--
ALTER TABLE `sales`
  ADD PRIMARY KEY (`id`),
  ADD KEY `idCheck` (`idCheck`);

--
ALTER TABLE `sales`
  MODIFY `id` int UNSIGNED NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=0;

BEGIN

DECLARE res INT;
DECLARE last_index INT;
SET @input := 'sales:  [  { id: 2, quantity: 5, price: 123, sum: 615 },  { id: 1, quantity: 9, price: 97, sum: 873 } ]';

SET @input:=REPLACE(@input, ' ', '');
SET @input:=REPLACE(@input, 'sales:', '');
SET @input:=REGEXP_REPLACE(@input, '([{,])([a-z])', '$1"$2');
SET @input:=REGEXP_REPLACE(@input, '([a-z]):', '$1":');

CREATE TEMPORARY TABLE new_tbl SELECT jtin.id AS jtin_id, jtin.quantity AS jtin_qty, pi.stock AS pi_qty, pi.price AS pi_price
FROM JSON_TABLE(@input,
                "$[*]"
                COLUMNS (id INT PATH "$.id" ,
                         quantity MEDIUMINT PATH "$.quantity",
                         price DECIMAL(7,2) PATH "$.price",
                         `sum` DECIMAL(8,2) PATH "$.sum"
                         )) AS jtin 
                LEFT JOIN prais_informations AS pi ON jtin.id  = pi.code;

SET res = (SELECT count(*) FROM new_tbl WHERE jtin_qty > pi_qty);

IF res = 0 THEN 

INSERT INTO checks(`data`, `user`) VALUES ( UNIX_TIMESTAMP(), 0);

SET last_index = LAST_INSERT_ID();
/*
  Инсертим содержимое массива заказа в таблицу регистрации
*/
INSERT INTO sales(`code`, `quantity`, `price`, `sum`, `idCheck`) SELECT nt.jtin_id, nt.jtin_qty, nt.pi_price, (nt.jtin_qty * nt.pi_price), last_index FROM new_tbl AS nt;

UPDATE prais_informations AS pi LEFT JOIN new_tbl ON pi.code = new_tbl.jtin_id SET pi.stock = pi.stock - new_tbl.jtin_qty;

END IF;

END