In my database there are 3 column which is Name, Age, Gender.
In the program, I only want to use 1 search button. When the button is clicked, the program determine which 3 of the textbox has input and search for the right data.
How do you work with the query? For example if Name and Gender has text, the query :
"Select * from table Where (Name = #name) AND (Gender = #gender)"
And when only name is entered, I only query for the name. Must I check textbox by textbox whether there is user input and then write multiple query for each of them? Or is there a better way to do this?
Edit (29/5/16) : I tried doing this another way like this
myCommand = New MySqlCommand("Select * from project_record Where
(FloatNo = #floatNo OR FloatNo = 'None') AND
(DevCompanyName = #devCompanyName OR DevCompanyName = 'None') AND
(DevType = #devType OR DevType = 'None') AND
(LotPt = #lotPt OR LotPt = 'None') AND
(Mukim = #mukim OR Mukim = 'None') AND
(Daerah = #daerah OR Daerah = 'None') AND
(Negeri = #negeri OR Negeri = 'None') AND
(TempReference = #tempRef OR TempReference = 'None')", sqlConn)
But as you can guess already it will not work efficiently as well because if I only enter input for DevType and leave other textboxes blank, the query will not pull up all the records for DevType only. It will just display as no records.
Select * from table
Where (Name = #name OR #name is Null)
AND (Gender = #gender OR #gender is Null)
...
it should be one query
Other answers have explained how to simplify the query. It is especially important to get rid of the ORs, since they inhibit any use of indexes.
Once you have the query build cleanly, you need to think about the dataset and decide which columns are usually used for filtering. Then make a few INDEXes for them. You won't be able to provide 'all' possible indexes, hence my admonition that you think about the dataset.
When building indexes, you can have single-column or multiple-column indexes. For your type of data, I would suggest starting with several 2-column indexes. Make sure each index starts with a different column.
For Where (Name = #name) AND (Gender = #gender), here are some notes:
INDEX(gender) is useless because of low 'cardinality';
INDEX(gender, name) might be useful, but the following would be better:
INDEX(name)
Things like name and DevCompanyName are virtually unique, so a 1-column index is probably good.
If you had gender and age, then INDEX(age, gender) might be useful.
MySQL will almost never use two indexes for a single SELECT.
By the way, the construction of the WHERE could be done in a Stored Procedure. You would need CONCAT, PREPARE, etc.
Original answer
(scroll down to see update)
Can you try the following:
build a list only including values of the textboxes that have an input
set a string of the join the items of that list together with the " AND " string
append that string to your standard SELECT statement
The code looks like this:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Predicate1 As String = Me.TextBox1.Text
Dim Predicate2 As String = Me.TextBox2.Text
Dim Predicate3 As String = Me.TextBox3.Text
Dim PredicateList As New List(Of String)
Dim WhereClause As String
Dim Query As String
If Predicate1 <> String.Empty Then
PredicateList.Add("Name=""" & Predicate1 & """")
End If
If Predicate2 <> String.Empty Then
PredicateList.Add("Age=""" & Predicate2 & """")
End If
If Predicate3 <> String.Empty Then
PredicateList.Add("Gender=""" & Predicate3 & """")
End If
WhereClause = String.Join(" AND ", PredicateList.ToArray)
Query = "SELECT * FROM TABLE WHERE " & WhereClause
MessageBox.Show(Query)
End Sub
Update
Further to the comments re SQL injection, here is an updated sample.
Dim Command As SqlClient.SqlCommand
Dim Predicate1 As String = Me.TextBox1.Text
Dim Predicate2 As String = Me.TextBox2.Text
Dim Predicate3 As String = Me.TextBox2.Text
Dim ParameterList As New List(Of SqlClient.SqlParameter)
Dim PredicateList As New List(Of String)
Dim BaseQuery As String = "SELECT * FROM TABLE WHERE "
If Predicate1 <> String.Empty Then
PredicateList.Add("name = #name")
ParameterList.Add(New SqlClient.SqlParameter("#name", Predicate1))
End If
If Predicate2 <> String.Empty Then
PredicateList.Add("age = #age")
ParameterList.Add(New SqlClient.SqlParameter("#age", Predicate2))
End If
If Predicate3 <> String.Empty Then
PredicateList.Add("gender = #gender")
ParameterList.Add(New SqlClient.SqlParameter("#gender", Predicate3))
End If
Command = New SqlClient.SqlCommand(BaseQuery & String.Join(" AND ", PredicateList.ToArray))
Command.Parameters.AddRange(ParameterList.ToArray)
COALESCE is your friend here. You can use it to make the where clause ignore comparisons where the parameter is NULL.
Select * from table Where (Name = COALESCE(#name,table.Name))
AND (Gender = COALESCE(#gender,table.Gender))
So, if the #name parameter is NULL, COALESCE(#name,table.Name) will return the value of the 'Name' column of the current row and (Name = COALESCE(#name,table.Name)) will always be true.
This assumes that if no value is entered in a textbox the corresponding parameter will be NULL. If instead it is a value such as 'None', you can use the NULLIF function to map 'None' to NULL
Select * from table Where
(Name = COALESCE( NULLIF( #name, 'None'), table.Name))
AND (Gender = COALESCE( NULLIF( #gender, 'None'), table.Gender))
How to implement a more efficient search?
The answer partly depends on what your definition of efficient is. I suspect you mean less code and fewer if blocks etc. But fundamentally, running a new SELECT * query to apply a filter is inefficient because your base data set can be all the rows and you just fiddle with the users View of it.
I have a DB with random data in columns for Fish, Color (string), Bird, Group (int) and Active which should be similar enough for Name, Age and Gender in the question - or that other long thing at the bottom.
DataTable
Fill a datatable and bind it to a DGV:
' form level object
Private dtSample As DataTable
...
' elsewhere
Dim sql = "SELECT Id, Name, Descr, `Group`, Fish, Bird, Color, Active FROM Sample"
Using dbcon As MySqlConnection = New MySqlConnection(MySQLConnStr)
' create SELECT command with the Query and conn
Dim cmd As New MySqlCommand(sql, dbcon)
...
daSample.Fill(dtSample)
daSample.FillSchema(dtSimple, SchemaType.Source)
End Using
dgv2.DataSource = dtSample
Going forward, we can filter the user's view of that table without issuing a new query.
Filter Controls
If some of the fields are limited to certain selections, for instance Gender, you can use a ComboBox instead of a TextBox. This is to help the user succeed and avoid typos (Make or Mael instead of Male; or here, correctly spelling Baracuda I mean Baraccuda, er Barracuda correctly.
For illustration purposes, Fish is something where the user can type in anything at all, but Bird is constrained to a set of choices. If there is a Bird table, cboBird can be bound or populated from it. But you may also be able to populate it from the master/base table:
Dim birds = dtSample.AsEnumerable.Where(Function(d) d.IsNull(5) = False).
Select(Function(d) d.Field(Of String)("Bird")).
Distinct.
ToArray()
cboBird.Items.AddRange(birds)
If "Finch" is a legal choice but there are none in the database, it wont show in the list. Depending on the app, this can be a Good Thing:
If the user filters on Finch and there a no resulting records, you won't need a MessageBox or StatusBar message explaining the empty result set.
If something is not in the list, you are signalling up front that there are none of those. It then becomes a matter of training why a known element isnt in the list.
On the other hand, you'd have to repopulate those filter controls each time before they are used in case new records were added recently. If the controls are on a Dialog or different TabPage, this is easy to do as needed.
It isnt always applicable, but it can help the user avoid typos.
It depends on the app whether either method is of value.
DBNull / 'none'
I am not sure why you are adding 'none' to each clause. If someone want to see all the 'John` or all the 'Cod' records, it doesn't seem like they would also be interested in 'none'. Personally, Null/DBNull seems a better way to handle this, but it is easy to add or not add either form.
It would seem more valuable to filter to just those with DBNull/None. The code above for the Bird List filters out DBNull and I would do so for none as well. Then, before the result is added to the ComboBox, add a `None' item first so it is at the top.
Again it depends on what the app does; Or = 'None', may make perfect sense in this case.
Filter
Using a TextBox for Fish and Group, a ComboBox for Bird and Color and a CheckBox for Active, the code can form the filter thusly:
Dim filterTerms As New List(Of String)
Dim filterFmt = "{0} = '{1}' "
' OR:
' Dim filterFmt = "{0} = '{1}' OR {0} Is Null"
' OR:
' Dim filterFmt = "{0} = '{1}' OR {0} = 'none'"
If String.IsNullOrEmpty(tbSearchFish.Text) = False Then
Dim txt = tbSearchFish.Text.Replace("'", "''")
filterTerms.Add(String.Format(filterFmt, "Fish", txt))
End If
If cboBird.SelectedIndex > -1 Then
filterTerms.Add(String.Format(filterFmt, "Bird", cboBird.SelectedItem.ToString))
End If
If String.IsNullOrEmpty(tbGroup.Text) = False Then
Dim n As Int32
If Int32.TryParse(tbGroup.Text, n) Then
filterTerms.Add(String.Format(filterFmt, "[Group]", n))
End If
End If
If cboColor.SelectedIndex > -1 Then
filterTerms.Add(String.Format(filterFmt, "Color", cboColor.SelectedItem.ToString))
End If
If chkActive.Checked Then
' NOTE: I do not have TreatTinyAsBoolean turned on
' for some reason
filterTerms.Add(String.Format(filterFmt, "Active", "1"))
End If
If filterTerms.Count > 0 Then
Dim filter = String.Join(" AND ", filterTerms)
dtSample.DefaultView.RowFilter = filter
Dim rows = dtSample.DefaultView.Count
End If
Use whichever filterFmt is appropriate for what the app needs to do
A filter term is only added to the list if the related control has a value (as per above, this could include a 'None').
For the TextBox, it escapes any embedded ticks such as might be found in names like O'Malley or D'Artgnan. It replaces one tick with two.
Since Group is a numeric, a valid Int32 input is tested
If there are elements in the filterTerms list, a filter string is created
The filter is applied to the DefaultView.Filter (you can use also use a DataView or a BindingSource) so that the code need not query the database to provide filter capabilities.
Rows will tell you how many rows are in the current View.
The only halfway tricky one is a Boolean like Gender or Active because those actually resolve to three choices: {Any/Either, A, B}. For that, I would use a ComboBox and ignore it for SelectedIndex 0 as well. I didn't bother with this because the Combo concept is amply covered. Result:
Is it More "Efficient"?
It still depends.
It doesn't re-query the database to get rows the app can already have.
No new DBConnection, DBCommand or other DBProvider objects are created, just a list.
No need to dynamically create a SQL statement with N parameters in a loop to avoid SQL injection/special words and chars.
It doesn't even query the database for the items for the filter terms. If there is a static list of them in the DB, they could be loaded once, the first time they use the filters.
It is easy to remove the filter, no need to query yet again without WHERE clauses.
A ComboBox where applicable helps the user find what they want and avoid typos.
Is the SQL "cleaner". more "efficient? The code doesn't really mess with new SQL, just some WHERE clauses.
Is there less code? I have no idea since we just see the result. It doesnt string me as a lot of code to do what it does.
In my database there are 3 column which is Name, Age, Gender. In the program, I only want to use 1 search button. When the button is clicked, the program determine which 3 of the textbox has input and search for the right data.
And when only name is entered, I only query for the name. Must I check textbox by textbox whether there is user input and then write multiple query for each of them? Or is there a better way to do this?
SELECT * FROM `table`
WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL);
With the above query if all text boxes have value, the result will not be one record (as if you where using logical AND between fields). If you want only that record you will filter it server-side with php from the rest of the results.
You can check the results on your own in this Fiddle
EDIT
In order to solve the above inconvenience (not bringing easily single results when needed) i got a little help from this answer and re-wrote the above query as:
SELECT *, IF(`name`=#name, 10, 0) + IF(`age`=#age, 10, 0) + IF(`gender`=#gender, 10, 0) AS `weight`
FROM `table`
WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL)
HAVING `weight`=30;
OR to still get all records with a weight on result
SELECT *, IF(`name`=#name, 10, 0) + IF(`age`=#age, 10, 0) + IF(`gender`=#gender, 10, 0) AS `weight`
FROM `table` WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL)
ORDER BY `weight` DESC;
You were pretty close. Let's look at
(FloatNo = #floatNo OR FloatNo = 'None')
So you want the field either to be the given input or 'None'? But there are (supposedly) no records in your table with FloatNo 'None'. What you really want to do is find out whether the input is none (i.e. empty):
(FloatNo = #floatNo OR #floatNo = '')
And for the case the user types in a blank by mistake, you can ignore this, too:
(FloatNo = #floatNo OR TRIM(#floatNo) = '')
The whole thing:
myCommand = New MySqlCommand(
"Select * from project_record Where
(FloatNo = #floatNo OR TRIM(#floatNo) = '') AND
(DevCompanyName = #devCompanyName OR TRIM(#devCompanyName) = '') AND
(DevType = #devType OR TRIM(#devType) = '') AND
(LotPt = #lotPt OR TRIM(#lotPt) = '') AND
(Mukim = #mukim OR TRIM(#mukim) = '') AND
(Daerah = #daerah OR TRIM(#daerah) = '') AND
(Negeri = #negeri OR TRIM(#negeri) = '') AND
(TempReference = #tempRef OR TRIM(#tempRef) = '')", sqlConn)
What is wrong with your approach?
Just change
(FloatNo = #floatNo OR FloatNo = 'None')
to
(FloatNo = #floatNo OR FloatNo = '' or FloatNo IS NULL)
And do that for every criteria.
Your query will respect empty values and NULL values after that.
I had a look at the other topics here on getting row numbers but couldn't fully understand them. All I need is a way of getting the total number of rows.
I have the following code that reads each row and populates a listbox, however as I want to assign that rows value to an array. I need to know the row number so I can use a 2-dimentional array, where each row data is stored separately in the array.
query = "SELECT * FROM bbs_test.test"
command = New MySqlCommand(query, Sqlconn)
reader = command.ExecuteReader
While reader.Read
arraynames = reader.GetString("data_array")
ListBox_displayarray.Items.Add(arraynames)
End While
Is there a way to get the total row number.
Please could any help
Thank you
After looking at the suggestions I have tried it out and this is how my code looks like
Sqlconn.Open()
Dim querycount As String
querycount = "SELECT count(*) FROM bbs_test.test"
command = New MySqlCommand(querycount, Sqlconn)
reader = command.ExecuteReader
While reader.Read
MessageBox.Show(reader.GetString("data_array"))
End While
The following error occurs
"An unhandled exception of type 'System.IndexOutOfRangeException' occurred in MySql.Data.dll
Additional information: Could not find specified column in results"
I checked and made sure the name of the column is data_array.
Could anyone help me please.
Use
query = "SELECT COUNT(*) FROM bbs_test.test"
This will fetch the count of total number of rows in your table
you need to run the query,
queryCount = "SELECT count(*) FROM bbs_test.test"
command = New MySqlCommand(queryCount, Sqlconn)
var totalRow = command.ExecuteScalar()
In variable totalRow , you have your no. of rows.
I am sure this is fairly simple put I am having trouble getting started on this. I use a Form to invoice clients which includes the field [Billing_Month]. What I'm looking to accomplish is this. When I create a new invoice, the [Billing_Month] will look to the last invoice created (use [Invoice_#] with DMax?), and populate the value from that that invoices [Billing_Month]
I have thought to use: Billing_Month = DMax ("Billing_Month", "frmInvoices"), but this doesn't specifically get me the last invoice, it would just look for the highest Billing_Month, which is a text field.
I have thought to use: Billing_Month = DLookup ("Billing_Month", "frmInvoices"), But this doesn't get me the last invoice to pull from.
I'd use a custom function for this - assuming the underlying table is called tblInvoices:
Function GetBillingMonthOfLatestInvoice()
Const SQL = "SELECT TOP 1 Billing_Month FROM tblInvoices ORDER BY [Invoice_#] DESC"
Dim RS AS DAO.Recordset
Set RS = CurrentDb.OpenRecordset(SQL)
If RS.EOF Then
GetBillingMonthOfLatestInvoice = Null
Else
GetBillingMonthOfLatestInvoice = RS(0)
End If
End Function
Update
The above code can be generalised to return other related fields like so:
Function GetValueForLatestInvoice(FieldToLookUp As String)
Dim RS As DAO.Recordset, SQL As String
SQL = "SELECT TOP 1 " + FieldToLookUp + " FROM tblInvoices ORDER BY [Invoice_#] DESC"
Set RS = CurrentDb.OpenRecordset(SQL)
If RS.EOF Then
GetValueForLatestInvoice = Null
Else
GetValueForLatestInvoice = RS(0)
End If
End Function
To use, copy the code to a new standard module, then for each relevant text box on the form, set its Default Value property in the Properties window to something like this:
=GetValueForLatestInvoice("Billing_Month")
That would be for the text box holding the billing month value; for the one holding the billing year, you would use
=GetValueForLatestInvoice("Billing_Year")
You can use a combination of both DLookup() and DMax() like so:
DLookup("Billing_Month","tblInvoices","[Invoice_#]=" & DMax("[Invoice_#]","tblInvoices"))
Good Afternoon to All,
I have a question concerning on SQL Queries. is it possible to use an array as a parameter to a query using the "IN" command?
for example,
int x = {2,3,4,5}
UPDATE 'table_name' set 'field' = data WHERE field_ID IN (x)
the reason I am asking this is to avoid an iterative SQL Statement when I have to update data in a database.
I also thought of using a for each statement in for the UPDATE Query but I don't know if it will affect the performance of the query if it will slow down the system if ever 100+ records are updated.
I am using VB.Net btw.
My Database is MySQL Workbench.
I have gotten the answer. I just simply need to convert each elements to a String then concatenate it with a "," for each element. so the parameter that i will pass will be a string.
ANSWER:
int x = {2,3,4,5}
will become
string x = "2,3,4,5"
My Query string will become "UPDATE tablename SET field=value WHERE ID IN("&x&")"
Thank you to all who helped.
If you have the query in a variable (not a stored procedure) and you don't have a huge amount of ids, you could built your own IN. I haven't tested the speed of this approach.
This code won't compile, it's just to give you an idea.
query = "SELECT * FROM table WHERE col IN ("
For t = 0 TO x.Length-1
If t > 0 Then query &= ","
query &= "#var" & t
Next
query &= ")"
...
For t = 0 TO x.Length-1
cmd.Parameters.Add("#var" & t, SqlDbType.Int).Value = x(t)
Next
i am not familiar with mySQL, but when dealing with MSSQL, I normally have a split function in DB so that I can use it to split concatenated integer values as a table, at VB side, something like:
Dim myIds = {1, 2, 3, 4}
Dim sql = <sql>
SELECT m.* FROM dbo.tblMyData m
INNER JOIN dbo.fncSplitIntegerValues(#Ids, ',') t ON t.id = m.Id
</sql>.Value
Using con As New SqlConnection("My connection string..."),
cmd As New SqlCommand(sql, con)
cmd.Parameters.Add("#Ids", SqlDbType.VarChar).Value =
myIds.Select(Function(m) m.ToString).Aggregate(Function(m, n) m & "," & n)
con.Open()
Dim rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
While rdr.Read()
Console.WriteLine(rdr.GetValue(0))
' do something else...
End While
End Using
dbo.fncSplitIntegerValues is a db function to split concatenated integer varchar into integer Id with given separator.
it's important not to use plain sql, instead, use sql parameters.
Note: above sample is not tested...
I have two tables which can be represented by this query (I have made this query the Recordsource of the form):
SELECT tblrcmtask.id, tblrcmtask.rcmtask,tblrcmtaskoptions.id,
tblrcmtaskoptions.rcm_id,
tblrcmtaskoptions.rcmtaskoptions
FROM tblrcmtask
INNER JOIN tblrcmtaskoptions
ON tblrcmtask.id=tblrcmtaskoptions.rcm_id
I want the user to be able to add new entries into these table via a form in access 2007.
Columns tblrcmtask.id and tblrcmtaskoptions.id are the primary keys of the tables tblrcmtask and tblrcmtaskoptions respectively.
I do not understand how do I create new ID in both the tables while the user adds new entries.The user can add only tblrcmtaskoptions.rcmtaskoptions and tblrcmtask.rcmtask in the form.Also, there are multiple rows in the table tblrcmtaskoptions for each tblrcmtask.id.
I want the user to be able to add new rows in the table tblrcmtaskoptions for an existing tblrcmtask.id
I tried using dropdowns for these two but I am facing problem while creating the new ID as Maximum of the ID + 1.
Dim MyRecords As DAO.Recordset
Dim Myfield As DAO.Fields
SQL = "SELECT Max(tblRCMTASK.ID) AS MaxOf_RCMTASKID FROM tblRCMTASK;"
Set MyRecords = dbTHIS.OpenRecordset(SQL)
Set Myfield = MyRecords.Fields
Me.txtRCMTASKID = Myfield("MaxOf_RCMTASKID") + 1
Me.txtRCMTASKID.DefaultValue = Myfield("MaxOf_RCMTASKID") + 1
MyRecords.Close
End If
Dim MyRecords1 As DAO.Recordset
Dim Myfield1 As DAO.Fields
SQL = "SELECT Max(tblRCMTASKOPTIONS.ID) AS MaxOf_RCMOPTIONSID FROM tblRCMTASK;"
Set MyRecords = dbTHIS.OpenRecordset(SQL)
Set Myfield1 = MyRecords1.Fields
Me.txtRCMOPTIONSID = Myfield1("MaxOf_RCMOPTIONSID") + 1
Me.txtRCMOPTIONSID.DefaultValue = Myfield("MaxOf_RCMOPTIONSID") + 1
MyRecords1.Close
I am getting an error which says you can't asign a value to this object and points to this line: Me.txtRCMTASKID = Myfield("MaxOf_RCMTASKID") + 1
How do I do this?
Access gives you trouble when trying to do operations on an autonumber field. If you would like to do these kinds of operations, you may be better off just using a regular number as a PK.
To get a recently inserted autonumber field to insert the same number in a related table, this is the VBA:
assuming recordset and database are declared, rs and db
dim id as integer
set db = CurrentDb
set rs = db.openrecordset("firstTable", dbOpenDynaSet)
With rs
.addNew
.Fields("field1").Value = Me.control1 'adds to column1 of your table the value of control1
.Fields("field2").Value = Me.control2
.update 'updates the record. If it is an autonumber, it will be automatically assigned. I will show you how to access this for your next insert
end with
'To get the autoID of the entry we just inserted, do this
id = db.OpenRecordSet("SELECT##IDENTITY")(0)
'Now you have the autoID of the recent insertion, so you may use it for your next one.
This is a classic form/subform set up. Create a form based solely on tblrcmtask with a subform tblrcmtaskoptions. The link child and master fields should be set to the common id. The wizards will do this for you. There is no code required. The id will be automatically added by the link fields.
You can see an example for in the 2007 version of the Northwind sample database.