How does MySQL specify how many pieces of data to query?

1. Create table test limit(id int ,value varchar(100));

2. Insert test data, a total of 6 records;

insert into test_limit values (1,'v1');

insert into test_limit values (2,'v2');

insert into test_limit values (3,'v3');

insert into test_limit values (4,'v4');

insert into test_limit values (5,'v5');

insert into test_limit values (6,'v6');

3. If you query the full data in the table, you can find a total of 6 data, select * from test limit t;

4. Write a statement and specify 3 pieces of data to be queried;

select * from test_limit limit 3;

1. Create table test limit(id int ,value varchar(100));

2. Insert test data, a total of 6 records;

insert into test_limit values (1,'v1');

insert into test_limit values (2,'v2');

insert into test_limit values (3,'v3');

insert into test_limit values (4,'v4');

insert into test_limit values (5,'v5');

insert into test_limit values (6,'v6');

3. Query the full data in the signal bend of the table, you can find a total of 6 data, select * from test limit t;

4. Write a statement to refer to the query of 3 pieces of data;

select * from test_limit limit 3;

The first 10 SQL statements of MySQL query are selected * from table name limit 0,10.

Usually 0 can be omitted, and it is written as limit to start from the end of the 0th record, that is, from the first record.

Use the select count(*)from table name; For query, the following is an example of querying the number of data entries named 111 in the database history

1. Enter mysql -u root -p on the command line, and then enter the mysql password to enter mysql

2. Enter use history to enter the history database3. Enter the statement select count(*)from 111; Query the total number of data records in **111.

4. As shown in the figure below, you can see that the total number of data records is 1744364

You can use the count function to view it.

For example, the name of the table is test.

You want to query how many records there are in the table.

select count(*)from test;

If you query by condition, you can use the where condition to select count(*)from test where id=1;