Add "IF NOT EXISTS" clause in MySQL and PostgreSQL export (#622)

Author: Pranay-Pandey

src/utils/exportSQL/generic.js

@@ -187,7 +187,7 @@ export function jsonToMySQL(obj) {
   return `${obj.tables
     .map(
       (table) =>
-        `CREATE TABLE \`${table.name}\` (\n${table.fields
+        `CREATE TABLE IF NOT EXISTS \`${table.name}\` (\n${table.fields
           .map(
             (field) =>
               `\t\`${
@@ -294,7 +294,7 @@ export function jsonToPostgreSQL(obj) {
                 )
                 .join("\n")}\n`
             : ""
-        }CREATE TABLE "${table.name}" (\n${table.fields
+        }CREATE TABLE IF NOT EXISTS "${table.name}" (\n${table.fields
           .map(
             (field) =>
               `${field.comment === "" ? "" : `\t-- ${field.comment}\n`}\t"${

src/utils/exportSQL/mysql.js

@@ -24,7 +24,7 @@ export function toMySQL(diagram) {
   return `${diagram.tables
     .map(
       (table) =>
-        `CREATE TABLE \`${table.name}\` (\n${table.fields
+        `CREATE TABLE IF NOT EXISTS \`${table.name}\` (\n${table.fields
           .map(
             (field) =>
               `\t\`${field.name}\` ${parseType(field)}${

src/utils/exportSQL/postgres.js

@@ -81,7 +81,7 @@ export function toPostgres(diagram) {
         )
         .join("\n");
 
-      return `CREATE TABLE "${table.name}" (\n${fieldDefinitions}${primaryKeyClause}${inheritsClause};\n\n${commentStatements}\n${indexStatements}`;
+      return `CREATE TABLE IF NOT EXISTS "${table.name}" (\n${fieldDefinitions}${primaryKeyClause}${inheritsClause};\n\n${commentStatements}\n${indexStatements}`;
     })
     .join("\n\n");