How can I combine these queries?

Question

I have 5 queries I'd like to join together. Basically what they do is they go though the database and select how much a tenant has paid, and how much a tenant owes based on how long ago he or she was charged.

I have four categories
Charge < 30 days old
Charge < 60 AND >= 30 days old
Charge < 90 AND >= 60 days old
Charge > 90 days old

I know how to get all those values separately, but how can I get them together, plus the amount the tenant has paid?

Here are my queries:
Amount the Tenant Has Paid

SELECT TransactionCode, TenantID, SUM(Amount) AS Paid FROM tblTransaction
WHERE Amount > 0
GROUP BY TransactionCode, TenantID

Charge is less than 30 days old

SELECT TransactionCode, TenantID, SUM(Amount) AS ChargedCurrent FROM tblTransaction
WHERE Amount < 0 AND TransactionDate > DATEADD("dd", -30, GETDATE())
GROUP BY TransactionCode, TenantID

Charge is less than 60 days old, but older than 29 days

SELECT TransactionCode, TenantID, SUM(Amount) AS ChargedOver30 FROM tblTransaction
WHERE Amount < 0 AND TransactionDate > DATEADD("dd", -60, GETDATE()) AND TransactionDate <= DATEADD("dd", -30, GETDATE())
GROUP BY TransactionCode, TenantID

Charge is less than 90 days old, but older than 59 days

SELECT TransactionCode, TenantID, SUM(Amount) AS ChargedOver60 FROM tblTransaction
WHERE Amount < 0 AND TransactionDate > DATEADD("dd", -90, GETDATE()) AND TransactionDate <= DATEADD("dd", -60, GETDATE())
GROUP BY TransactionCode, TenantID

Charge is older than 89 days

SELECT TransactionCode, TenantID, SUM(Amount) AS ChargedOver90 FROM tblTransaction
WHERE Amount < 0 AND TransactionDate <= DATEADD("dd", -90, GETDATE())
GROUP BY TransactionCode, TenantID

How can I get these all with one query?

Answer 1

It can be done like this:

SELECT TransactionCode, TenantID, 
SUM(CASE WHEN Amount > 0 then Amount ELSE 0 END) AS Paid,
SUM(CASE WHEN Amount < 0 AND TransactionDate > DATEADD("dd", -30, GETDATE()) THEN Amount ELSE 0 END) AS ChargedCurrent,  
SUM(CASE WHEN Amount < 0 AND TransactionDate > DATEADD("dd", -60, GETDATE()) AND TransactionDate <= DATEADD("dd", -30, GETDATE()) THEN Amount ELSE 0 END) AS ChargedOver30
SUM(CASE WHEN Amount < 0 AND TransactionDate > DATEADD("dd", -90, GETDATE()) AND TransactionDate <= DATEADD("dd", -60, GETDATE()) then Amount Else 0 END) AS ChargedOver60,
SUM(CASE WHEN Amount < 0 AND TransactionDate <= DATEADD("dd", -90, GETDATE()) THEN Amount ELSE 0 END) AS ChargedOver90 
FROM tblTransaction
GROUP BY TransactionCode, TenantID