of ORA-6502: PL/SQL: numeric or value error: NULL index table key value in Package IBY_FNDCPT_TRXN_PUB Procedure Create_Authorization. Authorization of credit card transaction failed The log correctly show COMMUNICATION_ERROR, and that is what AR user is expecting to see to know there was ...
1.创建表的时候创建索引 CREATE TABLE table_name [cok_name data_type] [UNIQUE|FULLTEXT|SPATIAL][INDEX|KEY][index_name](col_name[length]) [ASC|DESC] 1. 2. 其中UNIQUE,FULLTEXT,SPATAIAL为可选参数,分别表示唯一索引,全文索引和空间索引 INDEX与KEY为同义词,两者作用相同,用来指定创建索引 col_name...
创建主键Create table t1(id int(200) zerofil primary key auto_increment , name char(20),age int(200),unsigned,pay float(7,2) default(18000)); 对已有字段设置主键:alter table t1 add id int(20) zerofill primary key auto_increment first; 删除主键:alter table 表名 drop primary key; 外键f...
Indexes can be unique or nonunique. Unique indexes guarantee that no two rows of a table have duplicate values in the key column or columns. For example, no two employees can have the same employee ID. Thus, in a unique index, one rowid exist...
MySQL supports to use index on column which contains null value(what’s different from oracle). MySQL 中支持在含有NULL值的列上使用索引,但是Oracle不支持。这就是我们平时所说的如果列上含有NULL那么将会使索引失效。 严格来说,这句话对于 MySQL 来说是不准确的。
entry.value = value; returnold; } } addEntry(hash, key, value, index); returnnull; } 通过Hashtable的put底层源码,我们可以看到,方法体内,首先就对value值进行的判空操作,如果为空则抛出空指针异常;其次在计算hash值的时候,直接调用key的hashCode()方法,若keynull,自然也会报空指针异常,因此,我们在调用...
CREATETABLEtb_unique2(idint,namevarchar(20),addrvarchar(30),ageint,PRIMARYkey(id),UNIQUEKEYcom_nameadrr(name,addr),KEYage(age)) 注:1 这里的KEY age(age)意为普通索引。可通过查看索引命令SHOW INDEX FROM tablename命令查看,详细的见查看索引部分。
测试2,包含NULL复合索引的查询,首先加一个复合索引 alter table t1 drop index a,add index idx_ab(a,b); 可以看到不管是指定 a is null ,或者指定 b is null ,都可以利用上索引 idx_ab(key_len 可以看出) 测试2: descselect*fromt1wherea=50andb>20;+---+---+---+---+---+---+---+--...
检查发现一个类似如下的语句出现错误:语句: ALTER TABLE `ATable` CHANGE COLUMN `Atxt` `Btxt` DECIMAL(18,6) NOT NULL DEFAULT...0;错误: ERROR 1138 (22004) at line 7: Invalid use of NULL value 原因: NOT NULL DEFAULT 0 ,表示不为空,默认赋值0,但想修改的表单中存在为...null的值解决方案...
Null is a special constraint of columns. The columns in table will be added null constrain if you do not define the column with “not null” key words explicitly when creating the table.Many programmers like to define columns by default because of the conveniences(reducing the judgement code ...