MySQL data type details

mysql> desc t2;
+-------+--------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| id | bit(1) | YES | | NULL | |
+-------+--------+------+-----+---------+-------+
1 row in set (0.00 sec)

mysql> insert into t2 values(1);
Query OK, 1 row affected (0.05 sec)

mysql> select * from t2;
+------+
|id|
+------+
| |
+------+
1 row in set (0.00 sec)

mysql> select bin(id),hex(id) from t2;
+---------+---------+
| bin(id) | hex(id) |
+---------+---------+
| 1 | 1 |
+---------+---------+
1 row in set (0.03 sec)

mysql> insert into t2 values(2);
ERROR 1406 (22001): Data too long for column 'id' at row 1
mysql> alter table t2 modify id bit(2);
Query OK, 1 row affected (0.67 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into t2 values(2);
Query OK, 1 row affected (0.03 sec)

mysql> select bin(id),hex(id) from t2;
+---------+---------+
| bin(id) | hex(id) |
+---------+---------+
| 1 | 1 |
| 10 | 2 |
+---------+---------+
2 rows in set (0.00 sec)

mysql> create table dt(d date,t time,dt datetime);
Query OK, 0 rows affected (0.23 sec)


mysql> insert into dt values(now(),now(),now());
Query OK, 1 row affected, 1 warning (0.05 sec)

mysql> select * from dt;
+------------+----------+---------------------+
| d | t | dt |
+------------+----------+---------------------+
| 2021-05-13 | 10:14:07 | 2021-05-13 10:14:07 |
+------------+----------+---------------------+
1 row in set (0.00 sec)

mysql> create table t(id1 timestamp);
Query OK, 0 rows affected (0.22 sec)

mysql> insert into t values(null);
Query OK, 1 row affected (0.05 sec)

mysql> select * from t;
+---------------------+
| id1 |
+---------------------+
| 2021-05-13 10:18:05 |
+---------------------+
1 row in set (0.00 sec)

mysql> alter table t add column id2 timestamp;
Query OK, 0 rows affected (0.48 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> show create table t \G;
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `id1` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `id2` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00'
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

ERROR:
No query specified

mysql> create table varc(v varchar(4),c char(4));
Query OK, 0 rows affected (0.20 sec)

mysql> insert into varc values('abc ','abc ');
Query OK, 1 row affected (0.03 sec)

mysql> select length(v),length(c) from varc;
+-----------+-----------+
| length(v) | length(c) |
+-----------+-----------+
| 4 | 3 |
+-----------+-----------+
1 row in set (0.01 sec)
mysql> select concat(v,'+'),concat(c,'+') from varc;
+---------------+---------------+
| concat(v,'+') | concat(c,'+') |
+---------------+---------------+
| abc + | abc+ |
+---------------+---------------+
1 row in set (0.00 sec)

mysql> create table bina(c binary(3));
Query OK, 0 rows affected (0.22 sec)

mysql> insert into t set c='a';
ERROR 1054 (42S22): Unknown column 'c' in 'field list'
mysql> insert into bina set c='a';
Query OK, 1 row affected (0.05 sec)

mysql> select *,hex(c),c='a',c='a\0',c='a\0\0' from bina;
+------+--------+-------+---------+-----------+
| c | hex(c) | c='a' | c='a\0' | c='a\0\0' |
+------+--------+-------+---------+-----------+
| a | 610000 | 0 | 0 | 1 |
+------+--------+-------+---------+-----------+
1 row in set (0.00 sec)

mysql> create table gend(gender enum('M','F'));
Query OK, 0 rows affected (0.20 sec)

mysql> insert into gend values('M'),('F'),('1'),(null);
Query OK, 4 rows affected (0.03 sec)
Records: 4 Duplicates: 0 Warnings: 0

mysql> select * from gend;
+--------+
|gender|
+--------+
| M |
| F |
| M |
| NULL |
+--------+
4 rows in set (0.00 sec)

mysql> create table st(col set('a','b','c','d'));
Query OK, 0 rows affected (0.20 sec)

mysql> insert into st values('a,b'),('a,d,a'),('a,c'),('a');
Query OK, 4 rows affected (0.03 sec)
Records: 4 Duplicates: 0 Warnings: 0

mysql> insert into st values('f');
ERROR 1265 (01000): Data truncated for column 'col' at row 1
mysql> insert into st values(null);
Query OK, 1 row affected (0.03 sec)

mysql> select * from st;
+------+
| col |
+------+
| a,b |
| a,d |
| a,c |
| a |
| NULL |
+------+
5 rows in set (0.00 sec)