In SAS (Statistical Analysis System), SQL is used as a programming language to interact with and manage relational databases. Some of the SQL options available in SAS include:
1. PROC SQL: PROC SQL is a SAS procedure that allows you to run SQL statements within a SAS program. With PROC SQL, you can perform a variety of tasks, such as creating tables, selecting data, joining tables, aggregating data, and updating data.
2. SAS/ACCESS to ODBC: SAS/ACCESS to ODBC is a SAS interface that allows you to connect to ODBC-compliant databases, such as Microsoft SQL Server, Oracle, and MySQL. Once connected, you can use SQL statements to query and manipulate the data in the remote database.
3. LIBNAME statement: The LIBNAME statement is used to assign a library reference to a database or schema. This allows you to reference the database in your SAS program using the library reference, rather than the full database name.
4. SQL pass-through facility: The SQL pass-through facility allows you to send SQL statements directly to a remote database, without going through the SAS engine. This can improve performance, particularly for complex queries or large data sets.
5. SQL procedure options: There are a number of options that can be used with the PROC SQL statement, such as the OUTOBS option to limit the number of output observations, or the FEEDBACK option to display information about the execution of the query.
How many types of joins in SQL?
In SQL, there are four main types of joins:
1. Inner Join: An inner join returns only the matching rows between two or more tables, based on a specified join condition. In other words, it only returns the records that have matching values in both tables.
2. Left Join: A left join returns all the records from the left table and the matching records from the right table, based on the join condition. If a record in the left table does not have a matching record in the right table, the result will contain NULL values for the right table columns.
3. Right Join: A right join returns all the records from the right table and the matching records from the left table, based on the join condition. If a record in the right table does not have a matching record in the left table, the result will contain NULL values for the left table columns.
Additionally, there is also a cross join or Cartesian product, which returns all possible combinations of rows between two or more tables. However, it does not require a join condition and is not typically used in practice due to its potentially large result set.
How to create table in SQL?
To create a table in SQL, you can use the CREATE TABLE statement. Here’s the basic syntax:
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
….
);
In this syntax, table_name is the name of the table you want to create. column1, column2, column3, etc. are the names of the columns you want to include in the table, and datatype is the data type for each column.
For example, to create a table named “employees” with columns for employee ID, first name, last name, and hire date, you could use the following SQL statement:
CREATE TABLE employees (
employee_id INT,
first_name VARCHAR(50),
last_name VARCHAR(50),
hire_date DATE
);
This would create a table with four columns: “employee_id” of type INT, “first_name” and “last_name” of type VARCHAR with a maximum length of 50 characters, and “hire_date” of type DATE. You can modify this basic syntax with additional clauses to specify additional options, such as constraints, indexes, or default values.
