title: ORA-01722: "invalid number" error while inserting data into table
body: <p>The scenario given to me as follows.
  Create employees with following columns;</p>
  
  <pre><code>·         EmpId
  ·         EmpName
  ·         EmpEmail
  ·         EmpDate
  </code></pre>
  
  <p>In OLTP I need to enter one record at a time and following validations are to be done at backend;</p>
  
  <pre><code>·         EmpId should have a sequence generator
  ·         No numeric values allowed in EmpName
  ·         EmpDate should be in format mm/dd/yyyy
  ·         Email Id should have following validations
  o   Should contain ‘@’ sign and it should be only one
  o   Should end with ‘.com’
  o   Email id should have more than 3 characters
  </code></pre>
  
  <hr>
  
  <p>for this i've created a table and sequence like this</p>
  
  <pre><code>create table emp_316599
    (EmpId number(6),
    EmpName varchar2(15)CONSTRAINT chk_EmpName 
       check(regexp_like(EmpName,'![0-9]+')),
    EmpEmail varchar2(15) CONSTRAINT chk_EmpEmail
      check((length(EmpEmail)&gt;3) and
        substr(EmpEmail,-4)='.com' and
              instr(EmpEmail,'@',1,2)=0),
    EmpDate varchar2(15) 
    CONSTRAINT chek_EmpDate
      check(EmpDate=to_char(EmpDate,'mm-dd-yyyy')));
  
    Table created.       
  
   create sequence Emp_SEQ
   increment by 1
   start with 1
   maxvalue 1000
   cache 20
  sequence created.
  </code></pre>
  
  <hr>
  
  <p>Here comes the problem.
  When i am trying to insert using the below command it is giving me the error.</p>
  
  <pre><code>insert into emp_316599 values(Emp_SEQ.NEXTVAL,'&amp;EmpName','&amp;EmpEmail','&amp;EmpDate');
  </code></pre>
  
  <p><strong>ORA-01722 invalid number</strong></p>
  
  <p>Please help me out.</p>
  
  <p>Work environment as follows
  DB:Oracle 11g,
  tool:plsql developer</p>
  
  <p>Thanks
  Kumar</p>