step 9 test

status-20X · May 15, 2024 · 66877a7 · 66877a7
1 parent 0992a61
commit 66877a7
Show file tree

Hide file tree

Showing 4 changed files with 139 additions and 26 deletions.
diff --git a/enrollment.csv b/enrollment.csv
@@ -2,4 +2,5 @@ student_id,course
 1,Mathematics
 1,Physics
 2,Chemistry
-3,Mathematics
+3,Mathematics
+5,Biology
diff --git a/src/index.js b/src/index.js
@@ -4,6 +4,106 @@ const fs = require("fs");
 const parseQuery = require("./queryParser");
 const readCSV = require("./csvReader");
 
+function performInnerJoin(data, joinData, joinCondition, fields, table) {
+  return data.flatMap((mainRow) => {
+    return joinData
+      .filter((joinRow) => {
+        const mainValue = mainRow[joinCondition.left.split(".")[1]];
+        const joinValue = joinRow[joinCondition.right.split(".")[1]];
+        return mainValue === joinValue;
+      })
+      .map((joinRow) => {
+        return fields.reduce((acc, field) => {
+          const [tableName, fieldName] = field.split(".");
+          acc[field] =
+            tableName === table ? mainRow[fieldName] : joinRow[fieldName];
+          return acc;
+        }, {});
+      });
+  });
+}
+
+function performLeftJoin(data, joinData, joinCondition, fields, table) {
+  return data.flatMap((mainRow) => {
+    const matchingJoinRows = joinData.filter((joinRow) => {
+      const mainValue = getValueFromRow(mainRow, joinCondition.left);
+      const joinValue = getValueFromRow(joinRow, joinCondition.right);
+      return mainValue === joinValue;
+    });
+
+    if (matchingJoinRows.length === 0) {
+      return [createResultRow(mainRow, null, fields, table, true)];
+    }
+
+    return matchingJoinRows.map((joinRow) =>
+      createResultRow(mainRow, joinRow, fields, table, true)
+    );
+  });
+}
+
+function getValueFromRow(row, compoundFieldName) {
+  const [tableName, fieldName] = compoundFieldName.split(".");
+  return row[`${tableName}.${fieldName}`] || row[fieldName];
+}
+
+function performRightJoin(data, joinData, joinCondition, fields, table) {
+  // Cache the structure of a main table row (keys only)
+  const mainTableRowStructure =
+    data.length > 0
+      ? Object.keys(data[0]).reduce((acc, key) => {
+          acc[key] = null; // Set all values to null initially
+          return acc;
+        }, {})
+      : {};
+
+  return joinData.map((joinRow) => {
+    const mainRowMatch = data.find((mainRow) => {
+      const mainValue = getValueFromRow(mainRow, joinCondition.left);
+      const joinValue = getValueFromRow(joinRow, joinCondition.right);
+      return mainValue === joinValue;
+    });
+
+    // Use the cached structure if no match is found
+    const mainRowToUse = mainRowMatch || mainTableRowStructure;
+
+    // Include all necessary fields from the 'student' table
+    return createResultRow(mainRowToUse, joinRow, fields, table, true);
+  });
+}
+
+function createResultRow(
+  mainRow,
+  joinRow,
+  fields,
+  table,
+  includeAllMainFields
+) {
+  const resultRow = {};
+
+  if (includeAllMainFields) {
+    // Include all fields from the main table
+    Object.keys(mainRow || {}).forEach((key) => {
+      const prefixedKey = `${table}.${key}`;
+      resultRow[prefixedKey] = mainRow ? mainRow[key] : null;
+    });
+  }
+
+  // Now, add or overwrite with the fields specified in the query
+  fields.forEach((field) => {
+    const [tableName, fieldName] = field.includes(".")
+      ? field.split(".")
+      : [table, field];
+    resultRow[field] =
+      tableName === table && mainRow
+        ? mainRow[fieldName]
+        : joinRow
+        ? joinRow[fieldName]
+        : null;
+  });
+
+  return resultRow;
+}
+
 function evaluateCondition(row, clause) {
   const { field, operator, value } = clause;
   switch (operator) {
@@ -42,30 +142,18 @@ async function executeSELECTQuery(query) {
 
   // Perform INNER JOIN if specified
   if (joinTable && joinCondition) {
-    const joinFilePath = `${joinTable}.csv`;
-    if (!fs.existsSync(joinFilePath)) {
-      throw new Error(`CSV file '${joinFilePath}' not found`);
+    const joinData = await readCSV(`${joinTable}.csv`);
+    switch (joinType.toUpperCase()) {
+      case "INNER":
+        data = performInnerJoin(data, joinData, joinCondition, fields, table);
+        break;
+      case "LEFT":
+        data = performLeftJoin(data, joinData, joinCondition, fields, table);
+        break;
+      case "RIGHT":
+        data = performRightJoin(data, joinData, joinCondition, fields, table);
+        break;
     }
-
-    console.log(`Reading join data from file: ${joinFilePath}`);
-    const joinData = await readCSV(joinFilePath);
-
-    data = data.flatMap((mainRow) => {
-      return joinData
-        .filter((joinRow) => {
-          const mainValue = mainRow[joinCondition.left.split(".")[1]];
-          const joinValue = joinRow[joinCondition.right.split(".")[1]];
-          return mainValue === joinValue;
-        })
-        .map((joinRow) => {
-          return fields.reduce((acc, field) => {
-            const [tableName, fieldName] = field.split(".");
-            acc[field] =
-              tableName === table ? mainRow[fieldName] : joinRow[fieldName];
-            return acc;
-          }, {});
-        });
-    });
   }
 
   // Apply WHERE clause filtering

diff --git a/src/queryParser.js b/src/queryParser.js
@@ -74,4 +74,27 @@ function parseWhereClause(whereString) {
   });
 }
 
-module.exports = parseQuery;
+function parseJoinClause(query) {
+  const joinRegex =
+    /\s(INNER|LEFT|RIGHT) JOIN\s(.+?)\sON\s([\w.]+)\s*=\s*([\w.]+)/i;
+  const joinMatch = query.match(joinRegex);
+
+  if (joinMatch) {
+    return {
+      joinType: joinMatch[1].trim(),
+      joinTable: joinMatch[2].trim(),
+      joinCondition: {
+        left: joinMatch[3].trim(),
+        right: joinMatch[4].trim(),
+      },
+    };
+  }
+
+  return {
+    joinType: null,
+    joinTable: null,
+    joinCondition: null,
+  };
+}
+
+module.exports = { parseQuery, parseJoinClause };
diff --git a/student.csv b/student.csv
@@ -1,4 +1,5 @@
 id,name,age
 1,John,30
 2,Jane,25
-3,Bob,22
+3,Bob,22
+4,Alice,24