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[数据库]MySQL Metadata


http://www.devart.com/dotconnect/mysql/docs/MetaData.html

In this overload first parameter is name of a collection, and second parameter is the array of restrictions to be applied when querying information. These restrictions specify which subset of the collection will be returned. The restrictions can include, for example, the database name (in this case, only collection elements belonging to this database will be returned) or the mask for the name of collection elements (only the elements satisfying this mask will be returned). The quantity and description of restrictions allowed for each metadata collection are represented in the table here. Their number can also be obtained from the return of the GetSchema() method. If the second parameter is null/Nothing, it is ignored.
Instead of specifying the metadata collection name as a string constant, you may use members of System.Data.DbMetaDataCollectionNames and Devart.Data.MySql.MySqlMetadataCollectionNames as the first GetSchema argument values. The members of these classes are the string fields, each field stores the corresponding metadata collection name. It is recommended to use these fields rather than manually input the collection names manually as the string constants because in case of using these fields, you will find misspellings at compile-time, and intellisense will show you all the available metadata collection names.
GetSchema Method Reference
The following table provides detailed information on metadata collections that can be retrieved using the GetSchema method, and restrictions that can be applied for them. If the restriction name is not specified, a default value is used. For example, the default values for the database, table, and collection element name restrictions are "mysql", "user", and "%" accordingly. Note that the Database property of the connection string does not affect the GetSchema method, and the database restriction should be specified any time you are interested in some database other than "mysql". Some collections may be not supported in older server versions. If you try to get metadata for unsupported collection you will get exception with message "Collection not defined".

 


Collection Name
Number of restrictions
Remarks
Arguments
2

Returns list of arguments for stored procedures and functions on the server.
Restrict it by database name and procedure name.
Columns
3

Returns list of columns, their type and some extra information.
GetSchema("Columns") returns list of columns in the table "user" in database "mysql".
Restricted by database name, GetSchema returns columns of table "user" if it can be found in the database.
The second restriction is name of a table that GetSchema method should search in.
At last, you can set column name pattern as described in "Tables" collection.
Databases
1

Lists all databases on the server.
When restricted by name mask, returns all databases that match the mask.
DatasourceInformation
0

Returns information about the data source.
DataTypes
0

Returns information about data types supported by the data source.
ForeignKeys
3

Returns list of foreign keys in the database.
The first restriction for this collection is name of a database.
The second restriction is table name mask.
The third restriction is the key pattern.

 

ForeignKeyColumns
2

Returns list of columns used by foreign keys in the database.
Restrict it with database name and table name.
Functions
2

Returns list of stored functions on the server.
Restrict it by database name and function name.
IndexColumns
4

Returns list of indexed columns in the database, their type and some extra information.
Restrict it with database name, table name, index name pattern, and column name pattern.
Indexes
3

Returns list of indexes and their details.
The first restriction is database name
The second restriction is table name
The last restriction is the index name pattern.

 

MetaDataCollections
0

Returns this list. Same as using GetSchema() method without parameters.

 

PrimaryKeys
2

Returns list of columns that participate in primary keys.
The first restriction for this collection is name of a database.
The second restriction is table name.
The last restriction is the key name pattern.

 

Procedures
2

Returns list of stored procedures on the server.
Restrict it by database name and procedure name.
ReservedWords
0

Lists all reserved words used in the server.
Restrictions
0

Returns list of possible restrictions and their default values for the metadata collections.
Tables
2

GetSchema("Tables") returns list of tables in "mysql" database.
The first restriction for this collection is name of a database. If specified, the method returns all tables within the database.
The second restriction is table name mask. You can use wildcards '%' (any number of characters) and '_' (one character) to retrieve names of tables that match the mask.

 

Triggers
2

Returns list of triggers in a database.
The first restriction for this collection is database name pattern.
The second restriction is trigger name pattern.

 

UDFs
1

Returns information about user-defined functions on the server.
You can specify name of the function as restriction.

 

UniqueKeys
2

Returns list of columns that participate in unique keys.
The first restriction for this collection is name of a database.
The second restriction is table name.
The last restriction is the key name pattern.

 

UserPrivileges
1

Lists all users and their privileges on the server.
When restricted by username, returns information about specific user.
Users
1

Lists all users on the server.
When restricted by username, returns information about specific user.
ViewColumns
3

Returns list of columns used by views in the database.
Restrict it with database name, table name and column name.
Views
2

GetSchema("Views") returns list of views in "mysql" database.
The first restriction for this collection is name of a database.
The second restriction is view name mask.