select * from T_Debt
–检索T_Debt表返回所有的数据,负载大

select FNumber,FPerson from T_Debt
–检索T_Debt表仅返回FPerson字段列,负载小

select FNumber as 编码 from T_Debt
select FNumber 编码 from T_Debt
–检索T_Debt表返回FNumber字段列并把FNumber列名显示为’编码’,AS语法可省略

select * from T_Debt where FNumber='002'
–根据条件检索T_Debt表仅返回FNumber字段等于’002′的数据

select * from T_Debt where FNumber='002' or FPerson='zerg'
–根据条件检索T_Debt表仅返回FNumber字段或者FPerson字段满足条件

数据汇总函数：
max() 计算字段最大值
min() 计算字段最小值
avg() 计算字段平均值
sum() 计算字段合计值
count() 统计数据条数

select max(FAmount) from T_Debt
–检索T_Debt表返回FAmount字段最大值,返回的数据列为虚拟列

select count(*) from T_Debt
select count(FAmount) from T_Debt
–如果FAmount字段所有数据总没有NULL空值，则上述2句语句效果相同，如果FAmount字段包含NULL空值，则count(*)结果大于count(FAmount)结果

select * from T_Debt order by FNumber/升序排列,无参默认
select * from T_Debt order by FNumber desc/降序排列
–检索T_Debt表返回结果根据FNumber字段排列

select * from T_Debt where FPerson like 'k%'
select * from T_Debt where FPerson like '_e___'
–检索T_Debt表返回FPerson字段,模糊过滤

select * from T_Debt where FPerson like '[kz]%'
select * from T_Debt where FPerson like 'k%' or FPerson like 'z%'
——————————————————————-
select * from T_Debt where FPerson like '[^kz]%'
select * from T_Debt where not(FPerson like 'k%') and not(FPerson like 'z%')
–检索T_Debt表返回FPerson字段，上述2种语句效果相同

select * from T_Debt where FPerson is null
select * from T_Debt where FPerson is not null
–空值检测，使用is，而不是’=’