SQL使用where子句规定选择的标准

问题：

学习使用SQL，已经使用

SELECT * FROM isocketsqdb.t_upgrade_info;

选择出要观察的列

upgrageID                                                              devMAC                                                           devName   userID version upgradeStatus upReqTime upDownTime upFileType

'0b14718b-790c-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.9', '9', '1389257838369', '1389259458116', '1'
'5f968a27-7905-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.90', '9', '1389254973673', '1389257658130', '1'
'25c03c8e-777b-11e3-92c3-001a4d2f084b', 'C756920F483355BC029D56E394058C77', '8C77', NULL, '0.9.90', '9', '1389085654927', '1389088964441', '1'
'eda09057-7903-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '10.9.90', '1', '1389254352982', '1389254435520', '1'
'a0cb85eb-779b-11e3-92c3-001a4d2f084b', '855816FFE149ABA178F98ABB44171578', '1578', NULL, '0.9.90', '9', '1389099605256', '1389253169526', '1'

想从这些行中将相同devName的行选出来。

解决办法：

1. 使用WHERE语句。

SELECT * FROM isocketsqdb.t_upgrade_info WHERE devName='9FF9';

结果出来了：

'0b14718b-790c-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.9', '9', '1389257838369', '1389259458116', '1'
'5f968a27-7905-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.90', '9', '1389254973673', '1389257658130', '1'
'eda09057-7903-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '10.9.90', '1', '1389254352982', '1389254435520', '1'

2. 注意：SQL 使用单引号来环绕文本值（大部分数据库系统也接受双引号）。如果是数值，请不要使用引号。

3. 使用where和like的组合，则可以使用SQL通配符进行检索。

SELECT * FROM isocketsqdb.t_upgrade_info WHERE devMac LIKE '%9FF9';

结果是：

'0b14718b-790c-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.9', '9', '1389257838369', '1389259458116', '1'
'5f968a27-7905-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '0.9.90', '9', '1389254973673', '1389257658130', '1'
'eda09057-7903-11e3-92c3-001a4d2f084b', '669B73655FB004E772ACF5787A4D9FF9', '9FF9', NULL, '10.9.90', '1', '1389254352982', '1389254435520', '1'

问题解决。