Task: Schema-Matching (source dataset: HXD)

Task: 
Please identify the matching columns between Table A and Table B. For each column in Table A, specify the corresponding column in Table B. If a column in A has no corresponding column in Table B, you can map it to null. Represent each column mapping using a pair of column headers in a list, i.e., [Table A Column, Table B column or null]. Provide the mapping for each column in Table A and return all mappings in a list.

No explanation and return the matching columns in a structured JSON format: {"column_mappings": <a list of column pairs>}.

TableA:
| ISO3   | Location         |   DataId | Indicator                                                                                                                |   Value |   Precision | CountryName   |   SurveyYear | SurveyId   | IndicatorId   |   ByVariableId | ByVariableLabel                |
|:-------|:-----------------|---------:|:-------------------------------------------------------------------------------------------------------------------------|--------:|------------:|:--------------|-------------:|:-----------|:--------------|---------------:|:-------------------------------|
| NGA    | North Central    |  1086377 | Children wasted                                                                                                          |    9.3  |           1 | Nigeria       |         2008 | NG2008DHS  | CN_NUTS_C_WH2 |              0 |                                |
| NGA    | Benue            |  1219616 | Postneonatal mortality rate                                                                                              |   48    |           0 | Nigeria       |         2013 | NG2013DHS  | CM_ECMR_C_PNR |          14003 | Ten years preceding the survey |
| NGA    | Southwest - 1990 |  1272289 | Child mortality rate                                                                                                     |   90    |           0 | Nigeria       |         1990 | NG1990DHS  | CM_ECMR_C_CMR |          14003 | Ten years preceding the survey |
| NGA    | South South      |  3178563 | Accepting attitudes - Female teacher who is HIV+ but not sick should be allowed to continue teaching in school (3) [Men] |   29.2  |           1 | Nigeria       |         2003 | NG2003DHS  | HA_AATT_M_FTC |              0 |                                |
| NGA    | Borno            |  1646209 | Gender parity index for net primary school attendance                                                                    |    1.06 |           2 | Nigeria       |         2013 | NG2013DHS  | ED_NARP_B_GPI |              0 |                                |
| NGA    | Kano             |  1648762 | Gender parity index for net primary school attendance                                                                    |    0.97 |           2 | Nigeria       |         2013 | NG2013DHS  | ED_NARP_B_GPI |              0 |                                |
| NGA    | South South      |  1662219 | Gender parity index for net secondary school attendance                                                                  |    1    |           2 | Nigeria       |         2003 | NG2003DHS  | ED_NARS_B_GPI |              0 |                                |
| NGA    | Ekiti            |  1282115 | Children stunted                                                                                                         |   19.2  |           1 | Nigeria       |         2013 | NG2013DHS  | CN_NUTS_C_HA2 |              0 |                                |
| NGA    | Delta            |  2883110 | Women receiving an HIV test and receiving test results in the last 12 months                                             |   10.8  |           1 | Nigeria       |         2013 | NG2013DHS  | HA_CPHT_W_T1R |              0 |                                |
| NGA    | Rivers           |  1345025 | Child mortality rate                                                                                                     |   40    |           0 | Nigeria       |         2013 | NG2013DHS  | CM_ECMR_C_CMR |          14003 | Ten years preceding the survey |

TableB:
| ISO3   |   DataId | Indicator                                             |   Value |   Precision | CountryName   |   SurveyYear | SurveyId   | IndicatorId   |   ByVariableId | ByVariableLabel   |
|:-------|---------:|:------------------------------------------------------|--------:|------------:|:--------------|-------------:|:-----------|:--------------|---------------:|:------------------|
| NGA    |   223263 | First sexual intercourse by exact age 22 [Men]        |    59.9 |           1 | Nigeria       |         2008 | NG2008DHS  | SX_SBAG_M_B22 |              0 |                   |
| NGA    |   462425 | First sexual intercourse by exact age 20 [Women]      |    76.1 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_SBAG_W_B20 |              0 |                   |
| NGA    |   335556 | First sexual intercourse by exact age 22 [Women]      |    78   |           1 | Nigeria       |         2008 | NG2008DHS  | SX_SBAG_W_B22 |              0 |                   |
| NGA    |   223030 | Median age at first sexual intercourse [Women]: 45-49 |    15.5 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_AAFS_W_M45 |              0 |                   |
| NGA    |   382447 | First sexual intercourse by exact age 25 [Men]        |    76.6 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_SBAG_M_B25 |              0 |                   |
| NGA    |   292214 | Recent sexual activity [Men]: Within the last year    |    13.5 |           1 | Nigeria       |         2018 | NG2018DHS  | SX_LSEX_M_1YR |              0 |                   |
| NGA    |   223022 | Median age at first sexual intercourse [Women]: 20-24 |    17.6 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_AAFS_W_M20 |              0 |                   |
| NGA    |   416126 | Women: Total                                          |   100   |           1 | Nigeria       |         1990 | NG1990DHS  | SX_LSEX_W_TOT |              0 |                   |
| NGA    |   383644 | Recent sexual activity [Men]: One or more years ago   |     7.1 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_LSEX_M_1PY |              0 |                   |
| NGA    |   223026 | Median age at first sexual intercourse [Women]: 40-44 |    15.6 |           1 | Nigeria       |         2003 | NG2003DHS  | SX_AAFS_W_M40 |              0 |                   |



source_headers: ISO3
DataId
Indicator
Value
Precision
CountryName
SurveyYear
SurveyId
IndicatorId
ByVariableId
ByVariableLabel
target_headers: ISO3
DataId
Indicator
Value
Precision
CountryName
SurveyYear
SurveyId
IndicatorId
ByVariableId
ByVariableLabel
column_mappings: ISO3
ISO3
DataId
DataId
Indicator
Indicator
Value
Value
Precision
Precision
CountryName
CountryName
SurveyYear
SurveyYear
SurveyId
SurveyId
IndicatorId
IndicatorId
ByVariableId
ByVariableId
ByVariableLabel
ByVariableLabel
output: {"column_mappings": [["ISO3", "ISO3"], ["Location", null], ["DataId", "DataId"], ["Indicator", "Indicator"], ["Value", "Value"], ["Precision", "Precision"], ["CountryName", "CountryName"], ["SurveyYear", "SurveyYear"], ["SurveyId", "SurveyId"], ["IndicatorId", "IndicatorId"], ["ByVariableId", "ByVariableId"], ["ByVariableLabel", "ByVariableLabel"]]}