SQLConnectionUsableQ
SQLConnectionUsableQ[conn]
tests whether or not queries may be issued on conn.
SQLConnectionUsableQ[conn,{sql,res}]
expects result res when issuing sql on conn.
更多信息和选项
- To use SQLConnectionUsableQ, you first need to load DatabaseLink using Needs["DatabaseLink`"].
- SQLConnectionUsableQ is a server-side test and initiates communication with the connection's target server, local or remote.
范例
打开所有单元关闭所有单元基本范例 (1)
If you find that the examples in this section do not work as shown, you may need to install or restore the example database with the "DatabaseLink`DatabaseExamples`" package, as described in Using the Example Databases.
Open a connection to a sample database:
Generalizations & Extensions (1)
SQLConnectionUsableQ issues a test query whose contents depend on the RDBMS conn is connected to. When using custom drivers, use the two-argument form to supply your own test:
Properties & Relations (1)
SQLConnectionUsableQ initiates server communication and is therefore a stronger test than SQLConnectionOpenQ. However, it will generally take longer to evaluate: