MySQL update with inner join taking too long

I have the following two tables CREATE TABLE tbl_products_temp ( cd_id INT(6) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT, cd_structure MEDIUMBLOB NOT NULL, cd_smiles TEXT NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', cd_formula VARCHAR(100) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', cd_molweight DOUBLE NULL DEFAULT NULL, cd_hash INT(11) NOT NULL, cd_timestamp DATETIME NOT NULL, cd_pre_calculated TINYINT(1) NOT NULL DEFAULT '0', iupac_name VARCHAR(600) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', price_currency VARCHAR(3) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', price1 DECIMAL(10,2) NULL DEFAULT NULL, price2 DECIMAL(10,2) NULL DEFAULT NULL, price3 DECIMAL(10,2) NULL DEFAULT NULL, last_update TIMESTAMP NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(), deleted_dt DATETIME NULL DEFAULT NULL, PRIMARY KEY (cd_id) USING BTREE, INDEX tbl_products_temp_hx (cd_hash) USING BTREE, INDEX tbl_products_temp_px (cd_pre_calculated) USING BTREE, INDEX idx_iupac_name (iupac_name) USING BTREE, INDEX idx_formula (cd_formula) USING BTREE, INDEX idx_molweight (cd_molweight) USING BTREE, INDEX idx_smiles (cd_smiles(100)) USING BTREE ) COLLATE='latin1_swedish_ci' ENGINE=MyIsam CREATE TABLE tbl_products_temp2 ( cd_id INT(6) UNSIGNED ZEROFILL NOT NULL AUTO_INCREMENT, cd_structure MEDIUMBLOB NOT NULL, cd_smiles TEXT NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', cd_formula VARCHAR(100) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', cd_molweight DOUBLE NULL DEFAULT NULL, cd_hash INT(11) NOT NULL, cd_timestamp DATETIME NOT NULL, cd_pre_calculated TINYINT(1) NOT NULL DEFAULT '0', iupac_name VARCHAR(600) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', price_currency VARCHAR(3) NULL DEFAULT NULL COLLATE 'latin1_swedish_ci', price1 DECIMAL(10,2) NULL DEFAULT NULL, price2 DECIMAL(10,2) NULL DEFAULT NULL, price3 DECIMAL(10,2) NULL DEFAULT NULL, last_update TIMESTAMP NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(), deleted_dt DATETIME NULL DEFAULT NULL, PRIMARY KEY (cd_id) USING BTREE, INDEX tbl_products_temp_hx (cd_hash) USING BTREE, INDEX tbl_products_temp_px (cd_pre_calculated) USING BTREE, INDEX idx_iupac_name (iupac_name) USING BTREE, INDEX idx_formula (cd_formula) USING BTREE, INDEX idx_molweight (cd_molweight) USING BTREE, INDEX idx_smiles (cd_smiles(100)) USING BTREE ) COLLATE='latin1_swedish_ci' ENGINE=MyIsam Table tbl_products_temp has 241633 rows. Table tbl_products_temp2 has 218380 rows. I'm trying the following update query but its taking forever. UPDATE tbl_products_temp INNER JOIN tbl_products_temp2 ON tbl_products_temp.iupac_name = tbl_products_temp2.iupac_name SET tbl_products_temp.price1 = tbl_products_temp2.price1, tbl_products_temp.price2 = tbl_products_temp2.price2, tbl_products_temp.price3 = tbl_products_temp2.price3, tbl_products_temp.price_currency = 'EUR' When I run explain using the following I get: explain select * from tbl_products_temp inner join tbl_products_temp2 on tbl_products_temp.iupac_name = tbl_products_temp2.iupac_name id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra -------------------------------------------------------------------------------------------------------------------------------------------- 1 | SIMPLE | tbl_products_temp2 | ALL | idx_iupac_name | (NULL) | (NULL) | (NULL) | 218380 | 1 | SIMPLE | tbl_products_temp | ref | idx_iupac_name | idx_iupac_name | 603 | mydb.tbl_products_temp2.iupac_name | 1 | Using where How can I speed up this update query?