You need a select statement with a join to the couse table (for the Course_name ). Group by 't_course'.name to use the COUNT (*) function Thanks for contributing an answer to Stack Overflow!
The result should be: Show activity on this post. Select all courses from your course Table, join the enrolment table and group by your course id. With count () you can select the number of Students To make it working not only in mySQL I added an aggregate function to the name column.
For example, if you have a group (1, 2, 3, 3, 4, 4) and apply the COUNT function, the result is 6. If you specify the DISTINCT keyword explicitly, only unique non-null values are considered.
Introduction to SQL COUNT function. The SQL COUNT function is an aggregate function that returns the number of rows returned by a query. You can use the COUNT function in the SELECT statement to get the number of employees, the number of employees in each department, the number of employees who hold a specific job, etc.
SELECT COUNT(column_name) counts the non-null values of column in the table. The total number of STU_DEPT values in above table are 7 but one of them is null. Since count(column_name) counts non-null values of the given column, thus the output is 6.
Use the COUNT aggregate function to count the number of rows in a table. This function takes the name of the column as its argument (e.g., id ) and returns the number of rows for this particular column in the table (e.g., 5).
SQL Server provides 5 Isolation levels to implement with SQL Transaction to maintain data concurrency in the database.
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To count the number of rows, use the id column which stores unique values (in our example we use COUNT(id) ). Next, use the GROUP BY clause to group records according to columns (the GROUP BY category above). After using GROUP BY to filter records with aggregate functions like COUNT, use the HAVING clause.
How to get multiple counts with one SQL query?SELECT distributor_id,COUNT(*) AS TOTAL,COUNT(*) WHERE level = 'exec',COUNT(*) WHERE level = 'personal'
The term LEVEL refers to a Pseudocolumn in Oracle which is used in a hierarchical query to identify the hierarchy level (parent->child) in numeric format. The LEVEL returns 1 for root row, 2 for child of root row and so on, as tree like structure. LEVEL must be used with CONNECT BY Clause.
In SQL there is a hierarchy of data in which the outer level is the schema or database. The database is made up of tables (which can be base or virtual tables). Each table is made up of a set of rows. These rows have no ordering, but all have the same structure, so it is proper set.
There are two levels of a constraint, namely: column level constraint. table level constraint.
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The COUNT () function is one of the most useful aggregate functions in SQL. Counting the total number of orders by a customer in the last few days, the number of unique visitors who bought a museum ticket , or the number of employees in a department, can all be done using the COUNT () function.
Here, we used “*” as the argument to the function, which simply tells SQL to count all the rows in the table.
The query returned 5 as the output because SQL counted one value of product_line for each row of the table. It is important to note that the COUNT () function does not account for duplicates by default. For instance, the products table has only two unique values for the product_line column – “Motorcycles” and “Classic Cars” – but our query still returned 5 as the value. So, if you want to count only the unique values in the table, you have to use the DISTINCT keyword with your COUNT () function.
In this query, SQL returns unique product lines as groups and the number of products in each product line as the count. However, because of the ORDER BY clause, the results are arranged in ascending order by the COUNT () function.
The GROUP BY clause in SQL is used to aggregate (group) data together in groups to help calculate aggregated metrics. Aggregate functions available in SQL are COUNT (), SUM (), AVG (), MIN (), and MAX (). These functions return a single value for multiple rows. Aggregation is important because it may not always be feasible for you to go through each row to generate insights.
One of the most useful aggregate functions in SQL is the COUNT () function. If you are new to SQL and want to learn about the various ways to use the COUNT () function with some practical examples, this article is for you.
In this query, since we explicitly specified the DISTINCT keyword in the argument to the COUNT () function, SQL counts only the unique values of product_line.
You can use MySQL function mysql_affected_rows () to get the number of records deleted or update or inserted after executing the query.
If you are displaying records of a table then at the same time you can display number of records. Here is the code .
In this part, you will see the usage of SQL COUNT () along with the SQL MAX ().
To get data of 'agent_code', and number of agents for each group of 'agent_code' from the orders table with the following conditions -