oracle操作字符串：拼接、替换、截取、查找、长度、判断详解编程语言

select '拼接'||'字符串' as str from dual 

select concat('拼接', '字符串') as str from dual 

select concat(concat('拼接', '多个'), '字符串') from dual 

select substr(to_char(sysdate, 'yyyy-mm-dd HH:mi:ss'), 12, 5) as time from dual

substr("ABCDEFG", 0); //返回：ABCDEFG，截取所有字符  
substr("ABCDEFG", 2); //返回：CDEFG，截取从C开始之后所有字符  
substr("ABCDEFG", 0, 3); //返回：ABC，截取从A开始3个字符  
substr("ABCDEFG", 0, 100); //返回：ABCDEFG，100虽然超出预处理的字符串最长度，但不会影响返回结果，系统按预处理字符串最大数量返回。  
substr("ABCDEFG", -3); //返回：EFG，注意参数-3，为负值时表示从尾部开始算起，字符串排列位置不变。

select substr('AAA-BBB',1,instr('AAA-BBB','-',-1)-1) 值 from dual;

select substr('AAA-BBB',instr('AAA-BBB','-',-1)+1) 值 from dual;

select INSTR('CORPORATE FLOOR','OR', 3, 2) as loc from dual 

select '替换字符串' as oldStr, replace('替换字符串', '替换', '修改') as newStr from dual

 length(nvl(字段,''))=1

SELECT SBXH, SFZJHM,  
        case 
　　     when length(nvl(XM,''))=1 then XM 
         when length(nvl(XM,''))=2 then substr(XM, 0, 1)||'*' 
　　     when length(nvl(XM,''))=3 then substr(XM, 0, 1)||'**' 
　　     when length(nvl(XM,''))=4 then substr(XM, 0, 1)||'***' 
　　     else substr(XM, 0, 1)||'****' 
　　   end XM, 
       DJXH, SDNF, DWMC, YNSE 
    FROM ZHZS_SEWSR T 
    WHERE YNSE > 120000.000000 AND DWMC IS NOT NULL AND SFZJHM LIKE '36%' 
    ORDER BY YNSE DESC