Execution Cycle in sql

 Execution Cycle it means Which error is  encounter  first?
  by Default Sql check following cycle:

                        1)  Null value

                        2)  Data-type Length

                        3)  Data-type

                        4)  Primary Key

                        5)  Unique Key

Please run step-by-step  below example:

1) Step-1 ,Create temp table and Insert value

        CREATE TABLE #temp
         (
             intGlcode INT PRIMARY KEY,
            varEmpName VARCHAR(15) NOT NULL,
            varLastName VARCHAR(15),
            intAge TINYINT,
            Emp_Code VARCHAR(5) UNIQUE
         )

        in above table intGlcode->Primary key fields, varEmpName ->inserting not null value     eilds,Emp_Code->insert Unique value fields

INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
        )
VALUES  (
          1,
          'Nirav',
          'Gandhi',
          18,
          '0001'
        ) 
2) Step-2 , insert data
INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
        )
VALUES  (
          1,
          NULL,
          'Gandhi',
          'abcd',
          '0001'
        )
  In above example check,  insert a null value in varEmpname and also insert 'abcd' value in intAge,both are wrong data, but when you are running above example in your screen first  'null' value error  generate.

3) Step 3,  DataType Length value       
INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
        )
VALUES  (
          1,
          'Niravasasasasasasasa',
          'Gandhi',
          'abcd',
          '0001'
        )
In above example check,  insert a large value in varEmpname and also insert 'abcd' value in intAge,both are wrong data, but when you are running above example in your screen first  'String or binary data would be truncated'   error  generate, because varEmpname datatype lenght on VARCHAR(15).
    
4) Step 4 --DataType     

INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
        )
VALUES  (
          1,
          'Nirav',
          'Gandhi',
          99999999,
          '0001'
        )
In above example check,  insert a 1  in intGlcode and also insert '9999999' value in intAge,both are wrong data, but when you are running above example in your screen first  'Arithmetic overflow error for data type tinyint, value = 99999999.'   error  generate, because intAge datatype- 'tinyint' here primary key error not Generated.

5) Step 5 --Primary key

INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
        )
VALUES  (
          1,
          'Nirav',
          'Gandhi',
          18,
          '0001'
        )
In above example check,  insert a 1  in intGlcode and also insert '0001' value in Emp_Code,both are wrong data, but when you are running above example in your screen first  'Violation of PRIMARY KEY constraint'   error  generate, because intGlcode is Primary key, here Unique key  error not Generated.

6) Step 6   --Unique
INSERT  INTO #temp
        (
          intGlcode,
          varEmpName,
          varLastName,
          intAge,
          Emp_Code
               
        )
VALUES  (
          2,
          'Nirav',
          'Gandhi',
          18,
          '0001'
               
        )
      --In above example Unique key error generated.
DROP TABLE #temp