ISNULLis a function specific to the SQL dialect, whileCOALESCEis a standard SQL function. The former behaves differently depending on the specific implementation. The second always returns the first non-NULLvalue, regardless of the database system in use. ...
postgres=#createtabletbl(idintprimarykey,infotext);CREATETABLEpostgres=#createtabletbl1(idintreferencestbl(id), infotext);CREATETABLEpostgres=# \d tblTable"public.tbl"Column|Type|Modifiers---+---+---id|integer|notnullinfo|text|Indexes: "tbl_pkey"PRIMARYKEY, btree (id) Referencedby:TABLE"tbl...
(casewhenrange < 4000then1whenrange < 10000then2else3end)); 字段的顺序将改变: 有了这个索引,根据谓词«model = 'Boeing 777-300'»进行搜索将会有效,但是根据谓词«class = 3»进行搜索则不会有效。 NULL值 btree访问方法会索引空值,并支持按条件is null和is not null进行搜索。 让我们考虑航班表...
代码语言:javascript 代码运行次数:0 运行 AI代码解释 create table"t_user"("id"bigserial notnull,"username"varchar(64)notnull,constraint t_user_pk primarykey(id));insert into t_uservalues(1,'ACGkaka'); 会话一: 执行update语句。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 begin;update ...
Example: How to Use CASE Expression as Equivalent of ISNULL? We will utilize the same table’s column to depict the working of the CASE expression: SELECTemp_bonus,CASEWHENemp_bonusISNULLTHEN0ELSEemp_bonusENDASmodified_emp_bonusFROMemp_details; ...
len, cstate->cur_lineno); /* * If enough inserts have queued up, then flush all * buffers out to their tables. */ if (CopyMultiInsertInfoIsFull(&multiInsertInfo)) CopyMultiInsertInfoFlush(&multiInsertInfo, resultRelInfo, &processed); /* * We delay updating the row counter and ...
第一第二个值都为null,则返回第三个不为null的值返回当前时间; 2.DECODE(); 用法1: decode(条件,值1,返回值1,值2,返回值2,...值n,返回值n,缺省值) 该函数的含义如下: IF 条件=值1 THEN RETURN(翻译值1) ELSIF 条件=值2 THEN RETURN(翻译值2) ...
5.查询结果,一个字段的内容叠加。其中无论@content,还是username,字段值都必须加isnull 处理否则。返回结果为空。 declare @content nvarchar(4000) select @content=isnull( @content+',','')+isnull(username,'') from users select @content as aa ...
如上,我们插入4条数据,一个NULL,一个空字符串,一个空格字符串和包含一个字符的字符串.下面我们看看在Oracle中的处理: SELECT id, content, CASE WHEN content IS NULL THEN 1 ELSE 0 END AS isnull, CASE WHEN content = '' THEN 1 ELSE 0 END AS isempty, ...
bool isnull; StringInfoData strinfo; /* we first convert char * to datum representation */ jsonb_datum = DirectFunctionCall1(jsonb_in, CStringGetDatum(myjson)); /* then, we convert it to Jsonb * */ jb = DatumGetJsonbP(jsonb_datum); ...