How to check the number of data items in mysql?

In mysql, you can use the COUNT() function to check the number of data records. The syntax is "SELECT COUNT(*) AS alias FROM data table name;"; the COUNT() function can count the records contained in the data table. The total number of rows, or the number of data rows contained in the returned column based on the query results.

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MySQL COUNT() function statistics records contained in the table The total number of rows, or the number of data rows contained in the column returned according to the query results. There are two ways to use it:

• COUNT(*) Calculate the total number of rows in the table, regardless of a certain The column has a numeric value or is empty.

• COUNT (field name) calculates the total number of rows under the specified column. Rows with null values ​​will be ignored during calculation.

[Example] Query the total number of rows in the tb_students_score table. The input SQL statement and execution results are as follows.

mysql> SELECT COUNT(*)
    -> AS students_number
    -> FROM tb_students_score;
+-----------------+
| students_number |
+-----------------+
|              10 |
+-----------------+
1 row in set (0.03 sec)

As you can see from the query results, COUNT(*) returns the total number of rows recorded in the tb_students_score table, no matter what the value is. The total number returned is named students_number.

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