UPDATE tableB
INNER JOIN tableA ON tableB.name = tableA.name
SET tableB.value = IF(tableA.value > 0, tableA.value, tableB.value)
WHERE tableA.name = 'Joe'
UPDATE tableB
INNER JOIN tableA ON tableB.name = tableA.name
SET tableB.value = IF(tableA.value > 0, tableA.value, tableB.value)
WHERE tableA.name = 'Joe'/* Update products position by it's brand's position (from options table)
with Considering the languages */
UPDATE products
INNER JOIN options ON products.brand = options.value
SET products.brand_position = IF(options.lang = products.lang, options.position, products.brand_position)
WHERE options.name = 'pro_brand';