```xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns4:query_definition xmlns:ns2="http://www.i2b2.org/xsd/cell/crc/psm/1.1/" xmlns:ns4="http://www.i2b2.org/xsd/cell/crc/psm/querydefinition/1.1/" xmlns:ns3="http://www.i2b2.org/xsd/cell/crc/psm/analysisdefinition/1.1/">
    <query_name>(t) Digesti-ALT (SGLiver FDigesti@16:26:00</query_name>
    <query_timing>ANY</query_timing>
    <specificity_scale>0</specificity_scale>
    <panel>
        <panel_number>1</panel_number>
        <panel_timing>ANY</panel_timing>
        <panel_accuracy_scale>100</panel_accuracy_scale>
        <invert>0</invert>
        <total_item_occurrences>1</total_item_occurrences>
        <item>
            <hlevel>2</hlevel>
            <item_name>Digestive system</item_name>
            <item_key>\\i2b2_DIAG\i2b2\Diagnoses\Digestive system (520-579)\</item_key>
            <item_icon>FA</item_icon>
            <tooltip>Diagnoses \ Digestive system</tooltip>
            <class>ENC</class>
            <item_is_synonym>false</item_is_synonym>
        </item>
    </panel>
    <panel>
        <panel_number>2</panel_number>
        <panel_timing>ANY</panel_timing>
        <panel_accuracy_scale>100</panel_accuracy_scale>
        <invert>0</invert>
        <total_item_occurrences>1</total_item_occurrences>
        <item>
            <hlevel>5</hlevel>
            <item_name>ALT (SGPT) (LOINC:1742-6)</item_name>
            <item_key>\\i2b2_LABS\i2b2\Labtests\LAB\(LLB16) Chemistry\(LLB25) Liver Function Tests\SGPT\LOINC:1742-6\</item_key>
            <item_icon>LA</item_icon>
            <tooltip>Labtests \ Chemistry \ Liver Function Tests \ ALT (SGPT) (Group:SGPT) \ ALT (SGPT) (LOINC:1742-6)</tooltip>
            <class>ENC</class>
            <item_is_synonym>false</item_is_synonym>
        </item>
    </panel>
    <subquery_constraint>
        <first_query>
            <query_id>Observation C</query_id>
            <join_column>STARTDATE</join_column>
            <aggregate_operator>ANY</aggregate_operator>
        </first_query>
        <operator>LESS</operator>
        <second_query>
            <query_id>Observation B</query_id>
            <join_column>STARTDATE</join_column>
            <aggregate_operator>FIRST</aggregate_operator>
        </second_query>
    </subquery_constraint>
    <subquery>
        <query_id>Observation C</query_id>
        <query_type>EVENT</query_type>
        <query_name>Observation C</query_name>
        <query_timing>SAMEINSTANCENUM</query_timing>
        <specificity_scale>0</specificity_scale>
        <panel>
            <panel_number>0</panel_number>
            <panel_timing>SAMEINSTANCENUM</panel_timing>
            <panel_accuracy_scale>100</panel_accuracy_scale>
            <invert>0</invert>
            <total_item_occurrences>1</total_item_occurrences>
            <item>
                <hlevel>3</hlevel>
                <item_name>Liver Function Tests</item_name>
                <item_key>\\i2b2_LABS\i2b2\Labtests\LAB\(LLB16) Chemistry\(LLB25) Liver Function Tests\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>Labtests \ Chemistry \ Liver Function Tests</tooltip>
                <class>ENC</class>
                <item_is_synonym>false</item_is_synonym>
            </item>
        </panel>
    </subquery>
    <subquery>
        <query_id>Observation B</query_id>
        <query_type>EVENT</query_type>
        <query_name>Observation B</query_name>
        <query_timing>SAMEINSTANCENUM</query_timing>
        <specificity_scale>0</specificity_scale>
        <panel>
            <panel_number>0</panel_number>
            <panel_timing>SAMEINSTANCENUM</panel_timing>
            <panel_accuracy_scale>100</panel_accuracy_scale>
            <invert>0</invert>
            <total_item_occurrences>1</total_item_occurrences>
            <item>
                <hlevel>2</hlevel>
                <item_name>Digestive system</item_name>
                <item_key>\\i2b2_DIAG\i2b2\Diagnoses\Digestive system (520-579)\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>Diagnoses \ Digestive system</tooltip>
                <class>ENC</class>
                <item_is_synonym>false</item_is_synonym>
            </item>
        </panel>
    </subquery>
</ns4:query_definition>

```

I want to find all patients who have a diagnosis related to the digestive system (ICD codes 520-579) and have had a liver function test (ALT or SGPT) performed, with the liver function test being performed after the diagnosis.