```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) Anemia, unspeciLymphocyte immu@00:51:15</query_name>
    <query_timing>ANY</query_timing>
    <specificity_scale>0</specificity_scale>
    <subquery_constraint>
        <first_query>
            <query_id>Observation A</query_id>
            <join_column>STARTDATE</join_column>
            <aggregate_operator>FIRST</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 A</query_id>
        <query_type>EVENT</query_type>
        <query_name>Observation A</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>4</hlevel>
                <item_name>Anemia, unspecified</item_name>
                <item_key>\\ICD10_ICD9\Diagnoses\(D50-D89) Dise~nx0c\(D60-D64) Apla~8sol\(D64) Other anemias\(D64.9) Anemia~8pgh\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>Diagnoses \ Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89)
 \ Aplastic and other anemias and other bone marrow failure syndromes (d60-d64) \ Other anemias \ Anemia, unspecified</tooltip>
                <class>ENC</class>
                <constrain_by_date>
                    <date_from>2020-01-01T00:00:00.000-05:00</date_from>
                </constrain_by_date>
                <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>4</hlevel>
                <item_name>Lymphocyte immune globulin anti-thymocyte</item_name>
                <item_key>\\i2b2_MEDS\i2b2\Medications\MUL\(LME169) immunologic agents\(LME171) immune globulins\lymphocyte immune globulin, anti-thymocyte\</item_key>
                <item_icon>FA</item_icon>
                <tooltip>medications \ immunologic agents \ immune globulins \ lymphocyte immune globulin anti-thymocyte</tooltip>
                <class>ENC</class>
                <item_is_synonym>false</item_is_synonym>
            </item>
        </panel>
    </subquery>
</ns4:query_definition>

```

I want to find patients with a diagnosis of Anemia, unspecified, who have not had a Lymphocyte immune globulin anti-thymocyte medication event within the same instance number as the anemia diagnosis. The time range for the query is any time and the specificity scale is set to 0. The first subquery is for Observation A, which is an event-type query with a specificity scale of 0, looking for Anemia, unspecified with a diagnosis code in the range of (D64.9). The second subquery is for Observation B, also an event-type query with a specificity scale of 0, looking for Lymphocyte immune globulin anti-thymocyte medication. The subquery constraint is a less than operator, comparing the start dates of the two events.