【操作步骤】(请填写详细的操作步骤): 建表 create table test(a int key,b int not null); 通过replace插入数据 replace into test values (1, null), (2,null); 【预期输出】: 合理退出(疑问:replace当有key冲突时,先delete再insert,ignore_null时忽略插入,是否也不应做delete操作?) 【实际输出】: ...
select *,replace(address,’九’,’十’) AS rep from test_tb where id in (4,6) 总结:联想到前面有讲过 使用IF(expr1,expr2,expr3) 及 CASE…WHEN…THEN…END 可以实现查询结果的别名显示, 但区别是:这两者是将查询结果值做整体的别名显示,而replace则可以对查询结果的局部字符串做替换显示(输出)。
选出字符长度 SELECT char_length(ip) FROM IP; 计算sin值 SELECT sin(1.57); 为日期添加一定时间 SELECT ADDDATE('1998-01-02', 3); 获取当前日期 SELECT CURDATE(); 获取当前时间 SELECT curtime(); 如果expr1=null,返回expr2,否则返回expr1 ifnull(expr1, expr2) 如果expr1=expr2,返回null,否则返回...
REPLACEworks exactly likeINSERT, except that if an old row in the table has the same value as a new row for aPRIMARY KEYor aUNIQUEindex, the old row is deleted before the new row is inserted. 从上述描述中不难看出:replace在遇到主键冲突或者唯一键冲突的时候,是先执行delete,然后再执行insert的...
if (null != str && !"".equals(str)) { System.out.println("not empty"); } 1. 2. 3. 每次都这么判断太不优雅了,可以使用主流的工具类 apache common 3中的StringUtils类 注意:isEmpty 和 isBlank 方法的区别 StringUtils.isEmpty(" ") // false ...
总结:联想到前面有讲过 使用IF(expr1,expr2,expr3) 及 CASE...WHEN...THEN...END 可以实现查询结果的别名显示, 但区别是:这两者是将查询结果值做整体的别名显示,而replace则可以对查询结果的局部字符串做替换显示(输出)。 三、更新替换 3.1 将address字段里的 “东” 替换为 “西” ,如下 ...
SQL NULL > IFNULL Function The IFNULL( ) function is available in MySQL and SparkSQL, and not in SQL Server, Oracle, or HiveQL (Hive SQL). This function takes two arguments. If the first argument is not NULL, the function returns the first argument. Otherwise, the second argument is...
if ( result ) { var str = ""; for ( var i=result.length-1; i>=0; i-- ) { str += result; } return str; } else { return "null"; } } alert(strM.replace(/\b(\w)+\b/g,change)); 正则表达式使用详解 简介 简单的
In PySpark both fillna() and fill() are used to replace missing or null values of a DataFrame. Functionally they both perform same. One can choose either of these based on preference. These are used mainly for handling missing data in PySpark. What happens if I use fillna() on a non-...
REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. 如果新插入行的主键或唯一键在表中已经存在,则会删除原有记录并插入新行;如果在表中不...