I have a mysql table which has a data structure as follows,
create table data(
....
name char(40) NULL,
...
)
But I could insert names which has characters more than 40 in to name field. Can someone explain what is the actual meaning of char(40)?
You cannot insert a string of more than 40 characters in a column defined with the type CHAR(40).
If you run MySQL in strict mode, you will get an error if you try to insert a longer string.
mysql> create table mytable ( c char(40) );
Query OK, 0 rows affected (0.01 sec)
mysql> insert into mytable (c) values ('Now is the time for all good men to come to the aid of their country.');
ERROR 1406 (22001): Data too long for column 'c' at row 1
If you run MySQL in non-strict mode, the insert will succeed, but only the first 40 characters of your string is stored in the column. The characters beyond 40 are lost, and you get no error.
mysql> set sql_mode='';
Query OK, 0 rows affected (0.00 sec)
mysql> insert into mytable (c) values ('Now is the time for all good men to come to the aid of their country.');
Query OK, 1 row affected, 1 warning (0.01 sec)
mysql> show warnings;
+---------+------+----------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------+
| Warning | 1265 | Data truncated for column 'c' at row 1 |
+---------+------+----------------------------------------+
1 row in set (0.00 sec)
mysql> select c from mytable;
+------------------------------------------+
| c |
+------------------------------------------+
| Now is the time for all good men to come |
+------------------------------------------+
1 row in set (0.00 sec)
I recommend operating MySQL in strict mode (strict mode is the default since MySQL 5.7). I would prefer to get an error instead of losing data.
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I am having trouble trying to set the PDD(patient death date) to null on PHPMYADMIN until such death date comes; also on the client end then I can check for NULL data to use it.
Could anyone suggest me a solution, please ?
patientnhs_no hospital_no sex name surname dob address pls pdd
1001001001 6000001 m john smith 1941-01-01 Bournmouth 1 0000-00-00
(PDD should be null if is alive or death date if died)
As the message error says, you need to Increase the length of your column to fit the length of the data you are trying to insert (0000-00-00)
EDIT 1:
Following your comment, I run a test table:
mysql> create table testDate(id int(2) not null auto_increment, pdd date default null, primary key(id));
Query OK, 0 rows affected (0.20 sec)
Insertion:
mysql> insert into testDate values(1,'0000-00-00');
Query OK, 1 row affected (0.06 sec)
EDIT 2:
So, aparently you want to insert a NULL value to pdd field as your comment states ?
You can do that in 2 ways like this:
Method 1:
mysql> insert into testDate values(2,'');
Query OK, 1 row affected, 1 warning (0.06 sec)
Method 2:
mysql> insert into testDate values(3,NULL);
Query OK, 1 row affected (0.07 sec)
EDIT 3:
You failed to change the default value of pdd field. Here is the syntax how to do it (in my case, I set it to NULL in the start, now I will change it to NOT NULL)
mysql> alter table testDate modify pdd date not null;
Query OK, 3 rows affected, 1 warning (0.60 sec)
Records: 3 Duplicates: 0 Warnings: 1
You are most likely pushing a string 'NULL' to the table, rather then an actual NULL, but other things may be going on as well, an illustration:
mysql> CREATE TABLE date_test (pdd DATE NOT NULL);
Query OK, 0 rows affected (0.11 sec)
mysql> INSERT INTO date_test VALUES (NULL);
ERROR 1048 (23000): Column 'pdd' cannot be null
mysql> INSERT INTO date_test VALUES ('NULL');
Query OK, 1 row affected, 1 warning (0.05 sec)
mysql> show warnings;
+---------+------+------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------+
| Warning | 1265 | Data truncated for column 'pdd' at row 1 |
+---------+------+------------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM date_test;
+------------+
| pdd |
+------------+
| 0000-00-00 |
+------------+
1 row in set (0.00 sec)
mysql> ALTER TABLE date_test MODIFY COLUMN pdd DATE NULL;
Query OK, 1 row affected (0.15 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> INSERT INTO date_test VALUES (NULL);
Query OK, 1 row affected (0.06 sec)
mysql> SELECT * FROM date_test;
+------------+
| pdd |
+------------+
| 0000-00-00 |
| NULL |
+------------+
2 rows in set (0.00 sec)
I have a mysql table with a decimal(16,2) field. Seems like the addition operation with another decimal(16,2) field string can cause the Data truncated for column x at row 1 issue, which raises exception in my django project.
I'm aware of multiplication or division operation of that field can cause this issue bacause the result is probably not fit in decimal(16,2) definition, but does the addition and subtraction operation the same?
My MySQL server version is 5.5.37-0ubuntu0.14.04.1. You can reproduce this issue from bellow:
mysql> drop database test;
Query OK, 1 row affected (0.10 sec)
mysql> create database test;
Query OK, 1 row affected (0.00 sec)
mysql> use test;
Database changed
mysql> create table t(price decimal(16,2));
Query OK, 0 rows affected (0.16 sec)
mysql> insert into t values('2004.74');
Query OK, 1 row affected (0.03 sec)
mysql> select * from t;
+---------+
| price |
+---------+
| 2004.74 |
+---------+
1 row in set (0.00 sec)
mysql> update t set price = price + '0.09';
Query OK, 1 row affected (0.05 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update t set price = price + '0.09';
Query OK, 1 row affected, 1 warning (0.03 sec)
Rows matched: 1 Changed: 1 Warnings: 1
mysql> show warnings;
+-------+------+--------------------------------------------+
| Level | Code | Message |
+-------+------+--------------------------------------------+
| Note | 1265 | Data truncated for column 'price' at row 1 |
+-------+------+--------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from t;
+---------+
| price |
+---------+
| 2004.92 |
+---------+
1 row in set (0.00 sec)
There are two problems:
You are not storing decimal values, you're trying to store string/varchar, which is converted into double value by mysql, for example following code does not give errors update t set price = price + 0.09; (even executed several times)
Anyway this code gives expected warning (note number) update t set price = price + 0.091; you can change it to update t set price = price + cast(0.091 as decimal(16,2)); of course with cast you can use string values too update t set price = price + cast('0.09' as decimal(16,2));
In my case problem occurs when I try to insert a decimal with 3 digits after the the dot like: 0.xxx on a column defined as DECIMAL(10,2)
I changed it to DECIMAL(10,3) OR used php to enter values like 0.xx on DECIMAL(10,2) table
Certainly a noobish question, but I got to ask: :-) Assuming a column of type varchar and length 255 and the longest string stored in a row at this column shold have length 200. What happens, if I altered the columns length to less then 200? Would the strings all get "cut"?
By default, it will allow you to alter the column, it will truncate strings longer than the new length, and it will generate a warning.
mysql> create table t (v varchar(20));
Query OK, 0 rows affected (0.06 sec)
mysql> insert into t values ('12345678901234567890');
Query OK, 1 row affected (0.00 sec)
mysql> alter table t modify column v varchar(10);
Query OK, 1 row affected, 1 warning (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 1
mysql> show warnings;
+---------+------+----------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------+
| Warning | 1265 | Data truncated for column 'v' at row 1 |
+---------+------+----------------------------------------+
1 row in set (0.00 sec)
mysql> select * from t;
+------------+
| v |
+------------+
| 1234567890 |
+------------+
1 row in set (0.00 sec)
If you have the SQL mode STRICT_ALL_TABLES or STRICT_TRANS_TABLES set, the warning becomes an error and the ALTER will fail.
mysql> alter table t modify column v varchar(10);
ERROR 1265 (01000): Data truncated for column 'v' at row 1
I've learned this along the way but can't figure out where I read it or heard it, as there is nothing I have found online supporting it, but I remember that when upgrading from mysql4.x to mysql5.x, one of the required changes was that the auto-increment field for inserts had to change from '' to NULL if it was included.
I know its not required to have in the insert anyway, but just for point of interest...
Mysql 4.x would allow:
INSERT INTO TABLE (table_id, name, location) VALUES ('', 'john', 'NY');
But mysql 5.x had to have:
INSERT INTO TABLE (table_id, name, location) VALUES (NULL, 'john', 'NY');
I can't find any information on mysql's site to support this, but I know for a fact it throws an error in mysql 5.x and know it worked with '' in 4.x, but where is this documented?
Both the 4.1 and 5.0 docs state that 0 or NULL is required:
No value was specified for the
AUTO_INCREMENT column, so MySQL
assigned sequence numbers
automatically. You can also explicitly
assign NULL or 0 to the column to
generate sequence numbers.
It does not matter, mysql internally still convert to integer
mysql> CREATE TABLE some_test ( id int(10) unsigned NOT NULL auto_increment, primary key(id));
Query OK, 0 rows affected (0.00 sec)
mysql> insert into some_test values ('');
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> show warnings;
+---------+------+------------------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------------------+
| Warning | 1264 | Out of range value adjusted for column 'id' at row 1 |
+---------+------+------------------------------------------------------+
1 row in set (0.00 sec)
mysql> select * from some_test;
+----+
| id |
+----+
| 1 |
+----+
1 row in set (0.00 sec)
However, I will suggest use 0 to avoid this warning
I notice a very weird problem in my code. I am inserting a value of 128 but in my database it says 127.
I'd like to look at the mysql general/query logs however i dont ever see any log files produce no matter what i do. I tried -l , -l with an absolute path and --general_log_file. No luck. I also used mysqladmin flush-logs. Still nothing
Are you using a signed TINYINT datatype by any chance?
CREATE TABLE my_table (id TINYINT);
Query OK, 0 rows affected (0.03 sec)
INSERT INTO my_table VALUES (128);
Query OK, 1 row affected, 1 warning (0.00 sec)
SELECT * FROM my_table;
+------+
| id |
+------+
| 127 |
+------+
1 row in set (0.00 sec)