exec创建游标
>> close(myconn)>> myconn=database('cdcol','mytest','deepfuture','com.mysql.jdbc.Driver','jdbc:mysql://localhost:3306/cdcol')
myconn =
Instance: 'cdcol'
UserName: 'mytest'
Driver: 'com.mysql.jdbc.Driver'
URL: 'jdbc:mysql://localhost:3306/cdcol'
Constructor: [1x1 com.mathworks.toolbox.database.databaseConnect]
Message: []
Handle: [1x1 com.mysql.jdbc.JDBC4Connection]
TimeOut: 0
AutoCommit: 'on'
Type: 'Database Object'>> mycurs=exec(myconn,'select * from cds')
mycurs =
Attributes: []
Data: 0
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: 0
>>helpexec
--- helpfor database/exec ---
exec Execute SQL statement and open Cursor
CURSOR = exec(CONNECT,SQLQUERY,QTIMEOUT) returns a cursor object
CONNECT is a database object returned by DATABASE. sqlQuery
is a valid SQL statement. Use FETCH to retrieve data associated
with CURSOR.
Example:
cursor = exec(connect,'select * from emp')
where:
connect is a valid database object.
'select * from emp' is a valid SQL statement that selects all
columns from the emp table.
See also fetch.
查询结果
fetch(mycurs)
ans =
Attributes: []
Data: {3x4 cell}
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: [1x1 com.mathworks.toolbox.database.fetchTheData]>> a=ans
>> a.Data
ans ='Beauty''Ryuichi Sakamoto'[1990][1][1x33 char]'Groove Armada'[2001][4]'Glee''Bran Van 3000'[1997][5]>> mydata=a.Data
mydata ='Beauty''Ryuichi Sakamoto'[1990][1][1x33 char]'Groove Armada'[2001][4]'Glee''Bran Van 3000'[1997][5]>> mydata{1,2}
ans =
Ryuichi Sakamoto
>> mydata{1,1}
ans =
Beauty
>> mydata{1,3}
ans =
1990
查询参数
>> cs='Beauty'
cs =
Beauty
>> mycurs=exec(myconn,['select * from cds where titel =''',cs,''''])
mycurs =
Attributes: []
Data: 0
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds where titel ='Beauty''
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: 0
>> myres=fetch(mycurs)
myres =
Attributes: []
Data: {'Beauty''Ryuichi Sakamoto'[1990][1]}
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds where titel ='Beauty''
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: [1x1 com.mathworks.toolbox.database.fetchTheData]>>
格式的配置
>> setdbprefs
DataReturnFormat: 'cellarray'
ErrorHandling: 'store'
NullNumberRead: 'NaN'
NullNumberWrite: 'NaN'
NullStringRead: 'null'
NullStringWrite: 'null'
JDBCDataSourceFile: ''
UseRegistryForSources: 'yes'
TempDirForRegistryOutput: 'C:\Users\DEEPFU~1\AppData\Local\Temp'
DefaultRowPreFetch: '10000'>>>>help setdbprefs
SETDBPREFS Set preferences for database actions for handling null values.
SETDBPREFS(P,V) sets the preferences for database actions. P is the
list of properties to be set and V is the corresponding value list.
SETDBPREFS(P) returns the property with its current setting.
SETDBPREFS returns the property list with all current values.
The valid properties are NullNumberRead, NullNumberWrite, NullStringRead,
NullStringWrite, DataReturnFormat, ErrorHandling and JDBCDataSourceFile.
The value for each property is entered as a string.
For example, the command
setdbprefs('NullStringRead','null')
translates all NULL strings read from the database into the string
'null'.
The command
setdbprefs({'NullStringRead';'NullStringWrite';'NullNumberRead';'NullNumberWrite'},...
{'null';'null';'NaN';'NaN'})
translates NULL strings read into the string 'null', NULL values to NaN. A NaN in the
data written to the database is translated to a NULL and a 'null' string is translated to
NULL.
The command setdbprefs('DataReturnFormat','cellarray') returns the data
in the cursor Data field as a cell array which is the default behavior.
Other values for DataReturnFormat are 'numeric'which returns the data
as a matrix of doubles and 'structure'which returns the data as a structure
with the fieldnames corresponding to the fetched fields.
The command setdbprefs('ErrorHandling','store') returns any error messages
to the object Message field and will cause the next function that uses the
object to return an error. This is the default behavior. Other values
for ErrorHandling are 'report'which causes any function encountering an error
to report the error and stop processing and 'empty'which causes the fetch
command to return the cursor Data field as [] when given a bad cursor object
resulting from exec.
The command setdbprefs('JDBCDataSourceFile','d:\work\datasource.mat')
sets the location of the JDBC data source information to the file
d:\work\datasource.mat. This enables the Visual Query Builder to use
both ODBC and JDBC data sources. The command setdbprefs('JDBCDataSourceFile','')
specifies that no JDBC data sources are being used by the Visual Query Builder.
A single input can be used if it is a structure with fields corresponding to the valid
preference names. Each field should contain a valid preferenc setting. For example,
p.DataReturnFormat ='cellarray';
setdbprefs(p)
带限制输入行数的fetch
>> mycurs=exec(myconn,'select * from cds')
mycurs =
Attributes: []
Data: 0
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: 0
>> myres=fetch(mycurs,1)
myres =
Attributes: []
Data: {'Beauty''Ryuichi Sakamoto'[1990][1]}
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: [1x1 com.mathworks.toolbox.database.fetchTheData]
字段相关属性
>> mycurs=exec(myconn,'select * from cds')
mycurs =
Attributes: []
Data: 0
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: 0
>> myres=fetch(mycurs)
myres =
Attributes: []
Data: {3x4 cell}
DatabaseObject: [1x1 database]
RowLimit: 0
SQLQuery: 'select * from cds'
Message: []
Type: 'Database Cursor Object'
ResultSet: [1x1 com.mysql.jdbc.JDBC4ResultSet]
Cursor: [1x1 com.mathworks.toolbox.database.sqlExec]
Statement: [1x1 com.mysql.jdbc.StatementImpl]
Fetch: [1x1 com.mathworks.toolbox.database.fetchTheData]
行数
>> rows(myres)
ans =
3
列数
>> cols(myres)
ans =
4
字段名
>> columnnames(myres)
ans ='titel','interpret','jahr','id'>>
列宽
1-3列的宽度
>> width(myres,1)
ans =
200
>> width(myres,2)
ans =
200
>> width(myres,3)
ans =
11
>>
指定列的属性
下面是第2列属性
>> attr(myres,2)
ans =
fieldName: 'interpret'
typeName: 'VARCHAR'
typeValue: 12
columnWidth: 200
precision: []
scale: []
currency: 'false'
readOnly: 'false'
nullable: 'true'
Message: []>>
或者
>> myattrs=attr(myres)
myattrs =
1x4 struct array with fields:
fieldName
typeName
typeValue
columnWidth
precision
scale
currency
readOnly
nullable
Message
>> myattrs(1)
ans =
fieldName: 'titel'
typeName: 'VARCHAR'
typeValue: 12
columnWidth: 200
precision: []
scale: []
currency: 'false'
readOnly: 'false'
nullable: 'true'
Message: []>>
