网上流传一组“精妙SQL语句”,里边有这样一个, 说明:显示文章、提交人和最后回复时间 SQL: select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b 可是我在mysql里执行之后,报以下错误: 1054 - Unknown column 'a.title' in 'where clause' 我觉得如果让我写的话,我会写成这样: select title,username,max(adddate) as adddate from table group by title 不明白网上流产版为什么要写成那样,是错误的吧,不然为何我执行不能通过
for (int i=1;i<=(lay+1)/2;i++) { for (int j=1; j<=i; j++) { System.out.print ("*"); } } 然后打下半部分: for (int i=1;i>(lay+1)/2;i++) { for (int j=1; j<=lay-i+1; j++) { System.out.print ("*"); } 可是打不出来。。 请指教。。希望从各种小错误中慢慢学习。。 这边是总得code: public class Demo5 { public static void main (String []args) { int lay=5;
for (int i=1;i<=(lay+1)/2;i++) { for (int j=1; j<=i; j++) { System.out.print ("*"); } } for (int i=1;i>(lay+1)/2;i++) { for (int j=1; j<=lay-i+1; j++) { System.out.print ("*"); }
这个执行结果是对的 mysql> select * from testpost a where a.adddate = (select max(adddate) from test post b where a.title = b.title) ; +-------+----------+------------+ | title | username | adddate | +-------+----------+------------+ | post1 | zj | 2009-01-02 | | post2 | zj | 2009-01-02 | +-------+----------+------------+ 2 rows in set (0.00 sec)
装了oracle或sql server的xdjms能不能给我验证一下这个sql有没有我mysql下报的错 误, SQL: select a.title,a.username,b.adddate from table a,(select max(adddate) adddate from table where table.title=a.title) b 另外请高人指点,我这个sql有什么不足之处, select * from testpost a where a.adddate = (select max(adddate) from testpost b where a.title = b.title)
L*Q
11 楼
打印换行,打印下三角要逆序 public class Demo5 { public static void main (String[] args) { int lay=9;
for (int i=1;i<=(lay+1)/2;i++) { for (int j=1; j<=i; j++) { System.out.print ("*"); } System.out.println (); } for (int i=1;i<=(lay-1)/2 ;i++) { for (int j=(lay-1)/2; j>=i; j--) { System.out.print ("*"); } System.out.println (); } } }
for (int i=1;i<=(lay+1)/2;i++) { for (int j=1; j<=i; j++) { System.out.print ("*"); } } 然后打下半部分: for (int i=1;i>(lay+1)/2;i++) { for (int j=1; j<=lay-i+1; j++) { System.out.print ("*"); } 可是打不出来。。 请指教。。希望从各种小错误中慢慢学习。。 这边是总得code: public class Demo5 { public static void main (String []args) { int lay=5;
for (int i=1;i<=(lay+1)/2;i++) { for (int j=1; j<=i; j++) { System.out.print ("*"); } } for (int i=1;i>(lay+1)/2;i++) { for (int j=1; j<=lay-i+1; j++) { System.out.print ("*"); }
public static void main(String[] args){ int layer=5; StringBuffer sb= new StringBuffer("*"); for(int i=0; i{ if(i<3) { System.out.println(sb); sb.append("*");} else { String s=sb.substring(0,layer-i).toString(); System.out.println(s);
}
} } }
f*y
23 楼
突然发现我写了大概一年了
Y*G
24 楼
public class App { public static void main(String[] args) { for (int i = -2; i <= 2; i ++) { for (int j = 0; j < 3 - Math.abs(i); j ++) { System.out.print("*"); } System.out.println(); } } }