Sep 16, 2019 1:51:47 PM 共368人围观 0人评论

# 案例一SELECT employees.last_name,employees.commission_pctFROMemployeesWHEREcommission_pct = null;# 案例二SELECT employees.last_name,employees.salaryFROMemployeesWHE......

Sep 16, 2019 1:32:21 PM 共366人围观 0人评论

# 案例一SELECTemployees.employee_idFROMemployeesWHEREemployees.employee_id = 100 and employees.employee_id = 120;# 案例二SELECTemployees.employee_idFROMemployeesWHERE......

Sep 16, 2019 1:24:37 PM 共315人围观 0人评论

# 案例一SELECTemployees.last_name,employees.salaryFROMemployeesWHEREemployees.last_name like '__n_l%'; # 第三个字符是n 第五个字符是l# 案例二# 转义方式一SELECTemployees.last_name,empl......

Sep 16, 2019 1:11:21 PM 共322人围观 0人评论

SELECTIFNULLemployees.commission_pct,0 as 奖金率,employees.commission_pctFROMemployees;# --------------------------------SELECTCONCATemployees.first_name,',',emplo......

Sep 16, 2019 12:58:36 PM 共309人围观 0人评论

SELECT CONCAT'a','n','o' as 查询字段拼接; # 字段拼接SELECT CONCATemployees.last_name,employees.first_name as 姓名 from employees; # 字段拼接 + 别名