to denote a primary key-to-foreign key relationship or an infinity symbol 
to denote the foreign key side of a one-to-many relationship.A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z
A function that generates a single value from a group of values, often used with Group By and Having clauses. Aggregate functions include Avg, Count, Max, Min, and Sum. Also known as a set function.
A query (SQL statement) that summarizes information from multiple rows by including an aggregate function such as Sum or Avg. For example, you can create a query that averages the contents of a price column. Aggregate queries can also display subtotal information by creating groups of rows that have data in common. An example would be a query that displays the average price of a book for each publisher.
An alternative name for a table or column in expressions. Aliases are often used to shorten the table or column name for subsequent references in code, prevent possible ambiguous references, or provide a more descriptive name in query output.
Of an action, that executes separately from other events or actions. Asynchronous actions are performed in such a way that other actions can be performed simultaneously. For example, in the Query Designer, queries are executed asynchronously. Because individual results are returned as they are found, you can view results or perform other actions while the query continues to search for additional results.
The server or engine in a database system. In general, back end refers to the system that is the repository for the data, in contrast to the client, which presents data to the user. In a client/server system, the back end is the server. In an integrated database system, such as Microsoft® Visual FoxPro™ or Microsoft® Excel, the back end is the core database functionality of the product. As a rule, the back end contains the code that handles not only data storage, but indexes, validation, triggers, referential integrity, and other database functions.
A command-line utility that copies Microsoft® SQL Server™ data to or from an operating-system file in a user-specified format.
A type of data column containing binary data such as graphics, sound, or compiled code.
A unique identifier for a row within a database table. A candidate (or surrogate) key can be made up of one or more columns. By definition, every table must have at least one candidate key (in which case it automatically becomes the primary key for a table), but it is possible for a table to have more than one candidate key (in which case one of them must be designated as the primary key). Any candidate key that is not the primary key is called an alternate key.
A text file that contains SQL statements for all changes made to a database, in the order in which they were made during an editing session. Each change script is saved in a separate text file with an .sql extension. The change script creates a record of the changes made to the database which can be applied back to the database at a later time via a tool such as isql.
Specifies data values that are acceptable in a column. You can apply check constraints to multiple columns and you can apply multiple check constraints to a single column. When a table is deleted, all check constraints are also deleted.
The portion of a database system or application that presents data to the user. As a rule, the client (or front end) does not perform any database functions; instead, the client sends requests for data to a server, and then formats and displays the results.
Contrast with server, and back end.
A type of application that has a local interface but accesses data on a remote server. The application distributes the work between the local machine (the client) and the server (the back end), depending on the strengths of the client and server products. Client/server systems are often very efficient because they minimize network traffic, and because each portion of the application can be optimized for its particular function.
A character set that a computer uses to interpret and display data properly. Code pages usually correspond to different platforms and languages and are used in international applications.
Compare with locale.
A location within a database table that stores a particular type of data (for example, the firstname column in the authors table of the pubs sample database). The logical equivalent of a field.
Individual columns have their own specifications as to data type (for example, binary, character, integer, and so on) and maximum length. These are called column properties.
Restriction placed upon the value that can be entered into a column or a row. For example, age cannot be < 0 or > 110.
Compare with check constraint, unique constraint.
Displays data for summarized values from a field in a table, and then groups them by two sets of facts; one down the left side and the other across the top of the datasheet.
A collection of information required to access a specific database. The collection includes a data source name (DSN) and logon information. Data connections are stored in a project and are activated when the user performs an action that requires access to the database.
For example, a data connection for a Microsoft® SQL Server™ database consists of the name of the database, the location of the server on which it resides, network information used to access that server, and a user ID and password.
A language, usually a part of a database management system, that is used to define all attributes and properties of a database, especially row layouts, column definitions, key columns (and, sometimes, keying methodology), file locations, and storage strategy.
An ODBC term for the entity that provides data; similar to the term back end.
An ODBC term for the collection of information used to connect your application to a particular ODBC database. The ODBC Driver Manager uses this information to create a connection to the database. A DSN can be stored in a file (a file DSN) or in the Windows® Registry (a machine DSN).
Compare with data connection.
A graphical representation of any portion of a database schema. A database diagram can be either a whole or partial picture of the structure of a database; it includes objects for tables, the columns they contain, and the relationships between them.
One of the components of a database: a table, index, trigger, view, key, constraint, default, rule, user-defined data type, or stored procedure.
A collection of one or more data connections (a database and the information needed to access that database). When you create a database project, you can connect to one or more databases through ODBC and view their components through a visual user interface that includes a Database Designer for designing and creating databases and a Query Designer for creating SQL statements for any ODBC-compliant database.
An SQL-specific query that contains Data Definition Language (DDL) statements. These are statements that allow you to create or alter objects (such as tables, indexes, views, and so on) in the database.
A character set that uses one or two bytes to represent a character, allowing more than 256 characters to be represented. DBCS character sets are typically used in environments that use ideographic writing systems, such as Japanese, Korean, and Chinese.
Database object that enables the database to insert a value into a column if the user does not explicitly enter one.
Compare with global default.
A query (SQL statement) that removes rows from one or more tables. For example, the following Delete query removes rows from the titles table if their pub_id column contains the value "0766":
DELETE FROM titles
WHERE pub_id = '0766'
The state of being connected to a back-end database, like Microsoft® SQL Server™, so that any changes you make to a database diagram automatically update your database when you save the diagram or selected objects in it.
A combination of features that allows the user to drag an item and drop it into another item using the mouse. An item can be a source (the item the user drags) or a target (the item on which the user drops a source).
A type of data connection that is created based on information in a data source name (DSN) but is stored as part of a project or application. DSN-less connections are especially useful for Web applications because they enable you to move the application from one server to another without recreating the DSN on the new server.
Compare with data connection, data source name.
A trigger that is created with an optional encryption parameter that encrypts the definition text and cannot be decrypted. Encryption makes the information indecipherable to protect it from unauthorized viewing or use.
Compare with trigger.
A join in which rows from two tables are combined and added to the result set when there are equal values in the joined columns. By default, the inner and outer join types in the Query Designer are equijoins.
A character used to indicate that another character in an expression is meant literally and not as an operator. For example, in SQL the character "%" is used as a wildcard character to mean "any number of characters in this position." However, if you want to search for a string such as "10%" (ten percent), you cannot specify "10%" alone as a search string, because the "%" would be interpreted to mean "any number of characters in addition to 10." By specifying an escape character, you can flag instances where you mean "%" as "percent" specifically. For example, if you specify the escape character "#", you can indicate a search string of "10#%" to mean "ten percent."
Compare with wildcard character.
Any combination of operators, constants, literal values, functions, names of columns, controls, and properties that result in a single value. In a query, you can use expressions anywhere that you can use a column name. In the Query Designer, you can use expressions as settings for many action and properties arguments, to set criteria or define calculated fields in queries, and to set conditions in macros. In the Database Designer, you can use expressions to define check constraints.
A location in a record where data is stored; used in some database systems to mean "column." Although the terms "field" and "column" have slightly different meanings in formal database theory, in most instances they are meant synonymously.
Stores connection information for a database in a file that's saved on your computer. The file is a text file with the extension .dsn. The connection information consists of parameters and corresponding values that the ODBC Driver Manager uses to establish a connection.
Compare with data source name.
Contrast with machine DSN.
An option that specifies how full the database should make each index page. The amount of empty space on an index page is important because when an index page fills up, the system must take time to split it to make room for new rows. Use a fill factor of zero (0) to accept the database default.
A set of criteria applied to records to show a subset of the records or to sort the records.
A column or combination of columns whose values match the primary key of some other table. A foreign key does not have to be unique; in fact, foreign keys are often in a many-to-one relationship to a primary key. Foreign key values should be copies of the primary key values; no value in the foreign key except NULL should ever exist unless the same value exists in the primary key. A foreign key may be NULL; if any part of a composite foreign key is NULL, the entire foreign key must be NULL.
A type of outer join in which all rows in all joined tables are included, whether they are matched or not. For example, a full outer join between titles and publishers shows all titles and all publishers, even those that have no match.
Compare with inner join, left outer join, and right outer join.
A default that is defined for a specific database and is shared by columns of different tables.
Compare with default.
A rule that is defined for a specific database and is shared by columns of different tables.
Compare with rule.
A database object that provides access to data in the rows of a table, based on key values. Indexes provide quick access to data and can enforce uniqueness on the rows in a table.
A join in which records from two tables are combined and added to a query's results only if the values of the joined fields meet certain specified criteria. For example, the default join between tables in Query Designer view is an inner join that selects records from both tables only when the values of the joined fields are equal.
Compare with outer join.
Any table, view, or database diagram used as an information source for a query. Some databases may make other input sources available; for example, if you are using the Oracle database server, you can use synonyms as input sources.
A query that copies specific columns and rows from one table to another or to the same table. For example, the following Insert query copies the contents of the title_id, title, type, and pub_id columns from the titles table to the archivetitles table:
INSERT INTO archivetitles
SELECT title_id, title, type, pub_id
FROM titles
A query (SQL statement) that creates a new row and inserts values into specified columns. For example, the following Insert Values query inserts a new row into the titles table:
INSERT INTO titles
title_id, title, type, pub_id, price)
VALUES ('BU0219', 'Web Page Design', 'business', '1389', 29.99)
As a verb, to combine the contents of two or more tables and produce a result set that incorporates rows and columns from each table. Tables are typically joined using data that they have in common. For example, you can join a titles and publishers table on a common pub_id column to produce a result set that contains both title information and publisher information.
As a noun, the process or result of joining tables, as in the term "inner join" to indicate a particular method of joining tables.
Compare with inner join, and outer join.
A comparison clause that specifies how tables are related via their join fields. The most common join condition is equivalence (an equijoin) in which the values of the join fields must be the same. For example, you can join the titles and publishers tables by finding values that match in their respective pub_id columns. However, any comparison operator can be part of a join condition.
A comparison operator in a join condition that determines how the two sides of the condition are evaluated and which records are returned. The most common comparison operator is equivalence (=).
A table that has associations with two other tables and is used indirectly as an association between those two tables. Also called linking table.
A column used to identify a record, often used as the index column for a table.
A type of outer join in which all rows from the first-named table (the left table, which appears leftmost in the JOIN clause) are included. Unmatched rows in the right table do not appear. For example, you can create a left outer join between titles and the publishers tables to include all titles, even those you don't have publisher information for.
Compare with inner join, outer join, and right outer join.
A table that has associations with two other tables and is used indirectly as an association between those two tables. Also called junction table.
The set of information that corresponds to a specific language and country. A locale indicates specific settings such as decimal separators, date and time formats, and character-sorting order.
Stores connection information for a database in the system registry. The connection information consists of parameters and corresponding values that the ODBC Driver Manager uses to establish a connection.
Compare with data source name.
Contrast with file DSN.
A query (SQL statement) that creates a new table and then creates rows in it by copying rows from an existing table. For example, the following make table query copies rows from the titles table to the titlesCooking table:
SELECT title_id, title, type, pub_id, price
INTO titlesCooking
FROM titles
WHERE type = 'cooking'
A relationship between two tables in which rows in each table have multiple matching rows in the related table. For example, a many-to-many relationship is possible between the authors table and the titles table in the pubs sample database because each author can have written many titles, and each title can have many authors. Many-to-many relationships are maintained by using a third table called a junction table.
A type of column containing long strings of unstructured text (typically more than 255 characters).
One of the components of a database: a table, index, trigger, view, key, constraint, default, rule, user-defined data type, or stored procedure. Also called a database object.
A standard protocol for database servers providing a common language for Windows® applications to gain access to a database on a network. You install ODBC drivers for various databases that enable you to connect to the databases and access their data.
A relationship between two tables in which a single row in the first table can be related to one or more rows in the second table, but a row in the second table can be related to only one row in the first table. A typical one-to-many relationship is between the publishers table and the titles table in the pubs sample database, in which each publisher can be related to several titles, but each title can be related to only one publisher.
A relationship between two tables in which a single row in the first table can be related to only one row in the second table, and a row in the second table can be related to only one row in the first table. This type of relationship is unusual. An example is the relationship between an employee table and a mailboxes table used to store information about email addresses in a company. The tables have a one-to-one relationship because each employee has one mailbox, and each mailbox is assigned to only one employee.
A join that includes records even if they do not have related records in the joined table. You can create three variations of an outer join to specify the unmatched rows to be included: left outer join, right outer join, and full outer join.
Compare with inner join.
A value given to a variable. A parameter acts as placeholder in a query or stored procedure that can be filled in when the query or stored procedure is executed. Parameters allow you to use the same query or stored procedure many times, each time with different values.
For example, you can create a query with a parameter for a last name, then when you run the query, have it prompt you for the last name to find. Parameters can be used for any literal value, and in some databases, for column references as well.
A query you can use to work directly with tables on a server that understands a dialect of SQL that is different from the SQL processed by the client application. You can use a pass-through query to return a snapshot of rows or execute non-row-returning commands.
Storage of objects and data structures that involves converting complex data structures into a format suitable for file storage. Persistent data is retained by the computer between sessions.
A column or combination of columns that uniquely identifies a row in a table. It cannot allow null values and must always have a unique index. A primary key is used to relate a table to foreign keys in other tables.
A named attribute of an object. Properties define object characteristics, such as size and name, or the state of an object, such as enabled or disabled. Properties can be set for tables, columns, indexes, constraints, keys, and relationships.
A tabbed dialog box where you can identify the characteristics of tables, relationships, indexes, constraints, and keys. Every object in a database diagram has a set of properties that determine the definition of a database object. Each set of tabs shows only the properties specific to the selected object. If multiple objects are selected, the property pages show the properties of the first object you selected.
A specific request or set of instructions for retrieving, modifying, inserting, or deleting data in a database.
A term used in some database systems to mean "row". Although record and row have slightly different meanings in formal database theory, in most instances they are meant synonymously.
Ensures that for each row in a foreign key table, a corresponding row exists in the primary key table. It also prevents a row in a primary key table from being deleted when a relationship exists to a foreign key table. In database diagrams, the relationship between tables must be deleted before primary key columns can be deleted.
A relationship from a column or combination of columns in a table to other columns in that same table. Reflexive relationships are used to compare rows within the same table. For example, you can create a reflexive relationship to find all publishers that are in the same city and have the same postal code. In queries, this is called a self-join.
A link between tables that references the primary key in one table to a foreign key in another table. The relationship line is represented in a database diagram by a solid line if referential integrity between tables is enforced, or a dashed line if referential integrity is not enforced for INSERT and UPDATE transactions. The endpoints of a relationship line show a primary key symbol to denote a primary key-to-foreign key relationship or an infinity symbol to denote the foreign key side of a one-to-many relationship.
A virtual table that is produced by a query, representing all the columns and rows returned by the query in the order you specified.
A type of outer join in which all rows in the second-named table (the right table, the one that appears rightmost in the JOIN clause) are included. Unmatched rows in the left table are not included. For example, a right outer join between titles and publishers tables will include all publishers, even those who have no titles in the titles table.
Compare with inner join, outer join, and left outer join.
In a table, a set of related columns of information that are treated as a unit and that describe a specific entity. A row is the logical equivalent of a record.
A database object that is bound to a column or to a user-defined data type and that specifies what data can be entered in that column.
Compare with global rule.
A description of a database to the database management system (DBMS), generated using the data definition language provided by the DBMS. A schema defines attributes of the database, such as tables, columns, properties.
Compare with database diagram.
A comparison clause used in a query to specify the rows to return or update. For example, you can use a search condition to specify that a query displays only the authors who live in London.
A query that returns rows into a result set from one or more tables. A Select query can contain specifications for the columns to return, the rows to select, the order to put the rows in, and how to group (summarize) information.
Contrast with Delete query, Insert query, and Update query, all of which change data in a table.
A join that compares rows within the same table. For example, you can use a self-join to find all publishers that are in the same city and have the same postal code. In database diagrams, a self-join is called a reflexive relationship.
A computer on a network that controls access to data.
Compare with client/server.
A function that generates a single value from a group of values, often used with Group By and Having clauses. Aggregate functions include Avg, Count, Max, Min, and Sum. Also known as an aggregate function.
Structured Query Language, a database query and programming language.
A precompiled collection of SQL statements and optional control-of-flow statements stored under a name and processed as a unit. Stored procedures are stored within a database; can be executed with one call from an application; and allow user-declared variables, conditional execution, and other powerful programming features.
A SELECT statement defined within a query. The result set of the embedded SELECT statement becomes part of the search condition for the second query. For example, the following query uses a subquery to find all suppliers in Sweden, then uses the results in a WHERE clause to find all products with the selected suppliers:
WHERE supplier_id IN
(SELECT supplier_id
FROM supplier
WHERE (country = 'Sweden'))
A selection of tables and the relationship lines between them that is part of a larger database diagram. This selection can be copied to a new database diagram. This is called subsetting the diagram.
A unique identifier for a row within a database table. A surrogate (or candidate) key can be made up of one or more columns. By definition, every table must have at least one surrogate key (in which case it automatically becomes the primary key for a table), but it is possible for a table to have more than one surrogate key (in which case one of them must be designated as the primary key). Any surrogate key that is not the primary key is called an alternate key.
A data structure containing a collection of rows (or records) that have associated columns (or fields). It is the logical equivalent of a database file.
A storage area reserved by the database to keep track of transactions made to the database.
A special form of a stored procedure that is carried out automatically when data in a specified table is modified. Triggers are often created to enforce referential integrity or consistency among logically related data in different tables.
A link between tables that references the primary key in one table to a foreign key in another table, and that doesn't check referential integrity during INSERT and UPDATE transactions. An unenforced relationship is represented in a database diagram by a dashed line.
A query that combines two tables by performing the equivalent of appending one table onto the other.
A constraint that enforces entity integrity on a non-primary key. It ensures no duplicate values are entered in the columns on which the constraint is placed. NULL values are allowed as long as rows are unique in the table.
A naming convention for files which provides a machine-independent means of locating the file. A UNC name will usually include a reference to a shared folder and file name accessible over a network rather than specifying a drive letter and path. For example, to access a database named Northwind.mdb on a shared directory named Samples on the computer called MyWorkstation, you could use the UNC name \\MyWorkstation\Samples\Northwind.mdb.
UNC naming conventions are particularly useful in Web-based applications because they allow reference to data that is not necessarily stored on a particular Web server.
A query (SQL statement) that changes the values in columns of one or more rows in a table. For example, the following Update query for the titles table adds 10% to the price of all books for a particular publisher:
UPDATE titles
SET price = price * 1.1
WHERE pub_id = '1389'
A definition of the type of data a column can contain. It is created by the user and defined in terms of existing system data types. Rules and defaults can be bound to user-defined data types but not to system data types.
A virtual table generated by a query whose definition is stored in the database. For example, a view might be defined as containing three out of five available columns in a table, created to limit access to certain information. Views can be treated as tables for most database operations, including Select queries, and under some circumstances, Update, Insert, and Delete queries. Any operations performed on views actually affect the data in the table or tables on which the view is based.
A character that represents one or more other characters. For example, in SQL you can use the wildcard character "%" to mean "any number of characters," and can use it to search for parts of a word. The following example shows a search condition that uses the wildcard character "%" to indicate all names words that begin with "Mac":
LIKE 'Mac%'
Compare with escape character.