Glossary: Glossary

Glossary

calculated column: in a query, a column that does not exist in any of the tables that are being queried, but which is created as a result of a column expression. See also column expression.
Cartesian product: a type of join that matches each row from each joined table to each row from all other joined tables. See also cross join and join.
column: in relational databases, a vertical component of a table. Each column has a unique name, contains data of a specific type, and has certain attributes. A column is analogous to a variable in SAS terminology.
column alias: a temporary, alternate name for a column. Aliases are optional and can be specified in the SQL procedure's SELECT clause to name or rename columns. An alias is one word. See also column.
column expression: a set of operators and operands that, when evaluated, result in a single data value. The resulting data value can be either a character value or a numeric value.
composite index: an index that locates observations in a SAS data set by examining the values of two or more key variables. See also index and simple index.
condition: in the SQL procedure, the part of the WHERE clause that contains the search criteria. In the condition, you specify which rows are to be retrieved.
cross join: a type of join that returns the product of joined tables. A cross join is functionally the same as a Cartesian product. See also Cartesian product and join.
DISTINCT: a keyword that causes the SQL procedure to remove duplicate rows from the output.
equijoin: a kind of join in the SQL procedure. For example, when two tables are joined in an equijoin, the value of a column in the first table must equal the value of the column in the second table in the SQL expression. See also join.
group: in the SQL procedure, a set of rows that all have the same combination of values for the columns that are specified in a GROUP BY clause.
index: in SAS software, a component of a SAS data set that contains the data values of a key variable or variables, paired with a location identifier for the observation that contains the value. The value/identifier pairs are ordered in a structure that enables SAS to search by a value of a variable. See also composite index and simple index.
in-line view: a query-expression that is nested in the SQL procedure's FROM clause. An in-line view produces a table internally that the outer query uses to select data. You save a programming step when you use an in-line view, because instead of creating a view and then referring to it in another query, you can specify the view in-line in the FROM clause. An in-line view can be referenced only in the query (or statement) in which it is defined. See also query-expression.
inner join: See join.
integrity constraints: a set of data validation rules that you can specify in order to restrict the data values that can be stored for a variable in a SAS data file. Integrity constraints help you preserve the validity and consistency of your data.
join: in the SQL procedure, the combination of data from two or more tables (or from two or more SAS data views) to produce a single result table. A conventional join, which is often called an inner join, returns a result table for all the rows in one table that have one or more matching rows in the other table or tables. See also outer join.
join criteria: the set of parameters that determine how tables are to be joined. Join criteria are usually specified in a WHERE expression or in an SQL ON clause. See also join and outer join.
missing value: in SAS, a term that describes the contents of a variable that contains no data for a particular row (or observation). By default, SAS prints or displays a missing numeric value as a single period, and it prints or displays a missing character value as a blank space. In the SQL procedure, a missing value is equivalent to an SQL NULL value.
natural join: a type of join that returns selected rows from tables in which one or more columns in each table have the same name and the same data type and contain the same value. See also join.
outer join: in the SQL procedure, an inner join that is augmented with rows that do not match any row from the other table or tables in the join. There are three kinds of outer joins: left, right, and full. See also join.
PROC SQL view: a SAS data set that is created by the SQL procedure. A PROC SQL view contains no data. Instead, it stores information that enables it to read data values from other files, which can include SAS data files, SAS/ACCESS views, DATA step views, or other PROC SQL views. The output of a PROC SQL view can be either a subset or a superset of one or more files. See also SAS data view.
query: a set of instructions that requests particular information from one or more data sources.
query-expression: in PROC SQL, one or more table-expressions that can be linked with set operators. The primary purpose of a query-expression is to retrieve data from tables, PROC SQL views, or SAS/ACCESS views. In PROC SQL, the SELECT statement is contained in a query-expression.
row: in relational database management systems, the horizontal component of a table. A row is analogous to a SAS observation.
SAS data file: a type of SAS data set that contains data values and descriptor information that is associated with the data. The descriptor information includes the data types and lengths of the variables as well as the name of the engine that was used to create the data. A PROC SQL table is a SAS data file. See also SAS data set and SAS data view.
SAS data set: a file whose contents are in one of the native SAS file formats. There are two types of SAS data sets: SAS data files and SAS data views. SAS data files contain data values in addition to descriptor information that is associated with the data. SAS data views contain only the descriptor information plus other information that is required for retrieving data values from other SAS data sets or from files that are stored in other software vendors' file formats.
SAS data view: a type of SAS data set that retrieves data values from other files. A SAS data view contains only descriptor information such as the data types and lengths of the variables (columns) plus other information that is required for retrieving data values from other SAS data sets or from files that are stored in other software vendors' file formats. SAS data views can be created by the SAS DATA step and by the SAS SQL procedure. See also SAS data set.
simple index: an index that uses the values of only one variable to locate observations. See also composite index and index.
SQL (Structured Query Language): a standardized, high-level query language that is used in relational database management systems to create and manipulate objects in a database management system. SAS implements SQL through the SQL procedure.
Structured Query Language: See SQL (Structured Query Language),
table: in the SQL procedure, a SAS data file. See also SAS data file.
union join: a type of join that returns all rows with their respective values from each input table. Columns that do not exist in one table will have null (missing) values for those rows in the result table. See also join.
view: a generic term (used by many software vendors) for a definition of a virtual data set (or table). The definition is named and stored for later use. A view contains no data; it merely describes or defines data that is stored elsewhere.
WHERE clause: in the SQL procedure, the keyword WHERE followed by one or more WHERE expressions.
WHERE expression: a type of SAS expression that specifies a condition for selecting observations for processing by a DATA step or a PROC step. WHERE expressions can contain special operators that are not available in other SAS expressions. WHERE expressions can appear in a WHERE statement, a WHERE= data set option, a WHERE clause, or a WHERE command.

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