how to Display half records from table? MYSQL

Like the other answers already explained LIMIT can't be dynamically set in a query.
But you can workaround it with a MySQL user variable in combination with PREPARE/EXECUTE..

SET @count = (SELECT COUNT(*)/2 FROM aadhar); 
SET @sql = CONCAT('SELECT * FROM aadhar LIMIT ', @count);

PREPARE q FROM @sql;
EXECUTE q;
DEALLOCATE PREPARE q;

Or (safest option)

SET @count = (SELECT COUNT(*)/2 FROM aadhar); 

PREPARE q FROM 'SELECT * FROM aadhar LIMIT ?';
EXECUTE q USING @count;
DEALLOCATE PREPARE q;

Extra warning

Please note that SQL is by definition orderless. Using LIMIT without ORDER BY is meaningless. SQL is free to return the records what matches in anny order it wishes without ORDER BY meaning running the same query twice might result in a different result.

Also it's better to use CEIL() or CAST() which converts a double into a int so the methodes will not error when the table has a odd number off records and generates SQL with a double like this SELECT * FROM aadhar LIMIT 1.500000000

see demo on how to do those

Not perhaps what you would like but- 'Within stored programs, LIMIT parameters can be specified using integer-valued routine parameters or local variables as of MySQL 5.5.6.' https://dev.mysql.com/doc/refman/5.5/en/select.html

IF you don't want to use dynamic sql or a stored procedure but you do have some way of ordering your table then row number simulation (pre version 8) or row_number window function (version 8 on) may help. Given

+-----+----------+
| id  | username |
+-----+----------+
|   1 | aaa      |
|   2 | Jane     |
|   3 | Ali      |
|   6 | Bruce    |
|   7 | Martha   |
|   8 | Sidney   |
|  10 | charlie  |
|  12 | Elisa    |
|  14 | Samantha |
|  15 | Hannah   |
|  16 | Hannah   |
|  17 | Kevin    |
| 999 | bob      |
+-----+----------+
13 rows in set (0.00 sec)

SELECT S.ID,S.USERNAME FROM
(
SELECT U.ID,U.USERNAME,
         @RN:=@RN+1 ROWNUMBER,
         (SELECT ROUND(COUNT(*)/2) FROM USERS) TOPN
FROM USERS U
CROSS JOIN (SELECT @RN:=0) R
ORDER BY U.ID 
) S
WHERE S.ROWNUMBER <= S.TOPN;

will result in

+----+----------+
| ID | USERNAME |
+----+----------+
|  1 | aaa      |
|  2 | Jane     |
|  3 | Ali      |
|  6 | Bruce    |
|  7 | Martha   |
|  8 | Sidney   |
| 10 | charlie  |
+----+----------+
7 rows in set (0.00 sec)

There is no provision in MySQL to select and show half of the total records in the table until unless you explicitly specify the scalar in LIMIT clause.

You can achieve this using variables.

SELECT  @s:=@s+1 id,a.*
FROM    aadhar a,
        (SELECT @s:= 0) AS s where @s < (SELECT count(*)/2 from aadhar a2)

Here '@s' is a variable and adding create id which is autoincremented. Where condition store half of your total records count and @s stop just after reaching the limit of half count of your record.

Try this:

select *  from aadhar limit ((select count(*) from aadhar)/2);

The count clause returns the number of records, and half of that value is taken in limit.

select * from (select ,row_number() over() as rowno from aadhar) a where a.rowno <= (select ceil(count()/2) from aadhar) ;