concat函数和concat_ws函数

# 主要考察concat函数，让字符串以特定分隔符连接起来
# concat函数和concat_ws函数的区别，前者分隔符在中间参数，后者分隔符是第一个参数
# select concat(last_name, "'", first_name) as name
# from employees;

# or
select concat_ws("'", last_name, first_name) as name
from employees;