alter user scott account unlock; 然后执行sqlplus scott/tiger,此时会要求你修改scott的新口令。 设置命令行支持空格 set sqlblanklines on 变量替代--变量替换,这个过程只安排一个执行计划,可提高执行效率 SQL> select * from dept where deptno = &t; 输入t 的值: 10 原值1: select * from dept where de...
select comm,nvl(comm,0) from emp; nullif(ex1,ex2): 值相等返空,否则返回第一个值 例:如果工资和佣金相等,则显示空,否则显示工资 select nullif(sal,comm),sal,comm from emp; coalesce: 返回列表中第一个非空表达式 select comm,sal,coalesce(comm,sal,sal*10) from emp; nvl2(ex1,ex2,ex3) : 如果...
在方括号表达式里,在[:和:]里面封装的字符类的名字代表属于该类的所有字符的列表。 标准的字符类名字是:alnum、 alpha、blank、 cntrl、digit、 graph、lower、 print、punct、 space、upper、 xdigit。 它们代表在ctype中定义的字符类。 一个区域可以会提供其他的类。字符类不能用做一个范围的端点。 方括号表达...
SQL中的NULLIF函数是如何工作的,它与填充缺失值有何关联? 在SQL查询中,填充缺失值是指在查询结果中将缺失的数据用特定的值进行填充,以便更好地展示数据或进行后续分析。下面是一些常见的方法来填充SQL查询中的缺失值: 使用NULL值填充:在SQL中,NULL表示缺失值。当查询结果中存在缺失值时,可以使用NULL来填充。NULL值...
declare v_expr1 INT:=100; v_expr2 INT:=100; BEGIN if nullif(v_expr1,v_expr2) IS NULL then dbms_output.put_line('二者相等'); else dbms_output.put_line('二者不等'); end if; END; --NVL(expr1,expr2):用于将NULL转变为实际值。 --如果expr1是NULL,则返回expr2,如果expr1不是NULL...
ID Ifn2Col Ifn3Col CoalesceCol IsnullCol NullifCol NvlCol1 value $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow")2 blank blank blank blank6 blank blank blank blank9 blank blank blank blank10 blank blank ...
SQL_SVE_NULLIF (Intermediate level) SQL_STANDARD_CLI_CONFORMANCE 3.0 An SQLUINTEGER bitmask enumerating the CLI standard or standards to which the driver conforms. The following bitmasks are used to determine which levels the driver complies with:SQL_SCC_XOPEN_CLI_VERSION1: The driver complies ...
Coalesce1() ID Ifn2Col Ifn3Col CoalesceCol IsnullCol NullifCol NvlCol 1 value $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow") $lb("Red","Orange","Yellow") 2 blank blank blank blank 6 blank blank blank blank 9 blank blank blank ...
SQL_SVE_NULLIF (Intermediate level) SQL_STANDARD_CLI_CONFORMANCE 3.0 An SQLUINTEGER bitmask enumerating the CLI standard or standards to which the driver conforms. The following bitmasks are used to determine which levels the driver complies with:SQL_SCC_XOPEN_CLI_VERSION1: The driver complies ...
SQL_SVE_NULLIF (Intermediate level) SQL_STANDARD_CLI_CONFORMANCE 3.0 An SQLUINTEGER bitmask enumerating the CLI standard or standards to which the driver conforms. The following bitmasks are used to determine which levels the driver complies with:SQL_SCC_XOPEN_CLI_VERSION1: The driver complies ...