MySQL Basic learning knowledge points

"Watch and learn"

1.mysql does not support top X usage and supports the limit x, Y usage;

2. Multi-Table Connection query
1. Table1 INNER join table2: Inner connection. Only the intersection rows of the two tables that are connected are displayed.
2. Table1 LEFT JOIN table2: outer connection. Displays all rows of the Table1, even if there are no matching rows in table2.
3. Table1 Right join table2: Left outer connection. Displays all rows of the table2, even if there are no matching rows in table1z.
4. Table1 Full JOIN table2: Even if the rows in Table1 do not match in table2, or the rows in Table2 do not match in Table1. It still returns all matching rows in two tables of Table1 and table2.

3. Type int (M)

1 bytes = 8 bit, a byte can represent a maximum of 2 of the length of the data 8 square, in the computer is 128 to 127

tinyint a byte, smallint two bytes, mediumint three bytes, int four bytes, BIGINT eight bytes.

BIT[M] Bit field type, M represents the number of bits per value, range from 1 to 64, if M is ignored, default is 1

MySQL Basic learning knowledge points