86. 如何查询数据库有多少表? - Y- t6 E0 x! F+ C8 |
sql>select * from all_tables; ; `# Y- I6 {* B2 l7 w. T
+ p% s5 a! s+ e( L: ?; F
87. 如何测试sql语句执行所用的时间? 7 y$ [1 B% \/ c* f: z* W
sql>set timing on ;
% f( u+ S% Z: Ysql>select * from tablename;
9 V, y' @/ F g) c+ U88. chr()的反函数是?
1 D2 h8 N2 T+ C: S% ?1 V2 z, Dascii()
( R0 ?) b) l* L q0 V1 H ?* C; Bselect char(65) from dual; 5 h' \' S. M9 ^1 t; Y4 S, r
select ascii(’a’) from dual; $ ?3 W$ M/ \+ k
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89. 字符串的连接 * n0 Y, z/ x6 Z6 [' S
select concat(col1,col2) from table ;
6 F/ C( ~' f) g; y" c. aselect col1||col2 from table ; $ q) j4 K' b5 s2 h5 J
) {8 q- c# m: V0 q# @
90. 怎么把select出来的结果导到一个文本文件中?
% h7 c! c; u; k6 b+ [sql>spool c:"abcd.txt; U' p. h3 `- l2 B- Q5 F
sql>select * from table;
. h: `6 q R/ _+ _sql >spool off; |