Querying multiple tables in Flask using sqlite3

问题

Can anyone please give me a simpler solution for this?

I'm trying to query four different tables in my database and iterating them with a very bizarre FOR pattern, within HTML.

All the time I get MemoryError because the database is huge.

Python script:

import sqlite3
con=sqlite3.connect('/home/sergiuster/Downloads/python/exportSQL.db', check_same_thread=False)
con.row_factory = sqlite3.Row

#QUERY MATERIALECARACT
cur = con.cursor()
cur.execute("SELECT MaterialeCaracteristici.CodProdus, MaterialeCaracteristici.Rollout, MaterialeCaracteristici.CatSezon, MaterialeCaracteristici.CodEAN, MaterialeCaracteristici.Descriere,MaterialeCaracteristici.Descriere, MaterialeCaracteristici.PretVz FROM MaterialeCaracteristici WHERE MaterialeCaracteristici.CodProdus LIKE 'VGF%' GROUP BY MaterialeCaracteristici.CodProdus")
row = cur.fetchall()

#QUERY STOC
cur2=con.cursor()
cur2.execute("SELECT StocTotal.CodProdus, Sum(StocTotal.Stoc) AS SumOfStoc FROM StocTotal WHERE StocTotal.CodProdus LIKE 'VGF%' GROUP BY StocTotal.CodProdus")
row2 = cur2.fetchall()

#QUERY VANZARI
cur3=con.cursor()
cur3.execute("SELECT dbo_VanzariCumulat.CodProdus,Sum(dbo_VanzariCumulat.Cant) AS SumOfCant FROM dbo_VanzariCumulat WHERE dbo_VanzariCumulat.CodProdus LIKE 'VGF%' AND dbo_VanzariCumulat.UnLg NOT LIKE 'SH-D101' GROUP BY dbo_VanzariCumulat.CodProdus")
row3 =cur3.fetchall()

#QUERY PA
cur4=con.cursor()
cur4.execute("SELECT dbo_PA.MTRL, dbo_PA.CodProdus, dbo_PA.PA FROM dbo_PA GROUP BY dbo_PA.MTRL, dbo_PA.CodProdus, dbo_PA.PA")
row4 =cur4.fetchall()


from flask import Flask, render_template, request
app = Flask(__name__)
app.debug = True

@app.route("/index")
def index():

    return render_template('index.html', object2 = row2, object = row, object3 = row3,object4 = row4)

html:

{% for obj in object %}

            VZ:
            {% for obj3 in object3 %}
              {% if obj3['CodProdus'] == obj['CodProdus'] %}
                          {{ obj3['CodProdus'] }}//
                          {{ obj3['SumOfCant']  | int}}<br>
              {% endif %}
            {% endfor %}

            STOC:
            {% for obj2 in object2 %}
              {% if obj2['CodProdus'] == obj['CodProdus'] %}
                          {{ obj2['CodProdus'] }}//
                          {{ obj2['SumOfStoc']  | int}}<br>
              {% endif %}
            {% endfor %}

            PA:
            {% for obj4 in object4 %}
              {% if obj4['CodProdus'] == obj['CodProdus'] %}
                  {{ obj4['CodProdus'] }}//
                  {{ obj4['PA']|round(2)|float}}<br>
                  {{(((obj['PretVz']/1.19)-obj4['PA'])/obj4['PA']*100)|round(2)|float}}%
              {% endif %}
           {% endfor %}
 {% endfor %}

Is there any way that I can use a function and call it from HTML so that it will go back to the python script and then return the value for SumOfStoc back in HTML?

Example below:

#QUERY MATERIALECARACT
cur = con.cursor()
cur.execute("SELECT MaterialeCaracteristici.CodProdus, MaterialeCaracteristici.Rollout, MaterialeCaracteristici.CatSezon, MaterialeCaracteristici.CodEAN, MaterialeCaracteristici.Descriere,MaterialeCaracteristici.Descriere, MaterialeCaracteristici.PretVz FROM MaterialeCaracteristici WHERE MaterialeCaracteristici.CodProdus LIKE 'VGF%' GROUP BY MaterialeCaracteristici.CodProdus")
row = cur.fetchall()



def query_stoc(cod):  // I want to use MaterialeCaracteristici.CodProdus in html and pass it into this function, then return another value with the help of this function, in HTML;
    #QUERY STOC
    cur2=con.cursor()
    cur2.execute("SELECT StocTotal.CodProdus, Sum(StocTotal.Stoc) AS SumOfStoc FROM StocTotal WHERE StocTotal.CodProdus =? GROUP BY StocTotal.CodProdus", (cod))
    row2 = cur2.fetchall()
    return row2['SumOfStoc']

I hope i'm understandable and not making a fool of myself. Any help appreciated!

Thank you.

回答1:

There are several things you can do to 1) increase efficiency and 2) simplify your current code:

First, an option is to create a class to handle the different database connections. The class can have property attributes that can query from a corresponding table. Second, instead of cursor.fetchall, which loads the entire source into memory, simply return the cursor, as you only need to iterate over the source once, in the template itself. Lastly, the class instance can be passed to the template as a single parameter:

class db_Connector:
   def __init__(self, _file = '/home/sergiuster/Downloads/python/exportSQL.db'):
      self.filename = '/home/sergiuster/Downloads/python/exportSQL.db'
      self.conn = sqlite3.connect(self.filename, check_same_thread=False).cursor()
   @property
   def materialecaract(self):
     return self.conn.execute("SELECT MaterialeCaracteristici.CodProdus, MaterialeCaracteristici.Rollout, MaterialeCaracteristici.CatSezon, MaterialeCaracteristici.CodEAN, MaterialeCaracteristici.Descriere,MaterialeCaracteristici.Descriere, MaterialeCaracteristici.PretVz FROM MaterialeCaracteristici WHERE MaterialeCaracteristici.CodProdus LIKE 'VGF%' GROUP BY MaterialeCaracteristici.CodProdus")
   @property
   def stoc(self):
     return self.conn.execute("SELECT StocTotal.CodProdus, Sum(StocTotal.Stoc) AS SumOfStoc FROM StocTotal WHERE StocTotal.CodProdus LIKE 'VGF%' GROUP BY StocTotal.CodProdus")
   @property
   def vanzari(self):
     return self.conn.execute("SELECT dbo_VanzariCumulat.CodProdus,Sum(dbo_VanzariCumulat.Cant) AS SumOfCant FROM dbo_VanzariCumulat WHERE dbo_VanzariCumulat.CodProdus LIKE 'VGF%' AND dbo_VanzariCumulat.UnLg NOT LIKE 'SH-D101' GROUP BY dbo_VanzariCumulat.CodProdus")
   @property
   def pa(self):
      return self.conn.execute("SELECT dbo_PA.MTRL, dbo_PA.CodProdus, dbo_PA.PA FROM dbo_PA GROUP BY dbo_PA.MTRL, dbo_PA.CodProdus, dbo_PA.PA")

Then, in the route from which you are serving your template:

@app.route("/index")
def index():
  return render_template('index.html', _object = db_Connector())

Now, in the template, simply call the proper attributes:

{%for obj in _object.materialecaract%}

        VZ:
      {% for obj3 in _object.vanzari%}
         {% if obj3['CodProdus'] == obj['CodProdus'] %}
                      {{ obj3['CodProdus'] }}//
                      {{ obj3['SumOfCant']  | int}}<br>
          {% endif %}
        {% endfor %}

        STOC:
        {% for obj2 in _object.stoc %}
          {% if obj2['CodProdus'] == obj['CodProdus'] %}
                      {{ obj2['CodProdus'] }}//
                      {{ obj2['SumOfStoc']  | int}}<br>
          {% endif %}
        {% endfor %}

        PA:
        {% for obj4 in _object.pa %}
          {% if obj4['CodProdus'] == obj['CodProdus'] %}
              {{ obj4['CodProdus'] }}//
              {{ obj4['PA']|round(2)|float}}<br>
              {{(((obj['PretVz']/1.19)-obj4['PA'])/obj4['PA']*100)|round(2)|float}}%
          {% endif %}
       {% endfor %}
{% endfor %}

回答2:

Forgot to add one thing:

{%for obj in _object.materialecaract%}

    VZ:
  {% for obj3 in _object.vanzari%}
     {% if obj3['CodProdus'] == obj['CodProdus'] %}
                  {{ obj3['CodProdus'] }}//
                  {{ obj3['SumOfCant']  | int}}<br>
      {% endif %}
    {% endfor %}

    STOC:
    {% for obj2 in _object.stoc %}
      {% if obj2['CodProdus'] == obj['CodProdus'] %}
                  {{ obj2['CodProdus'] }}//
                  {{ obj2['SumOfStoc']  | int}}<br>
      {% endif %}
    {% endfor %}

    PA:
    {% for obj4 in _object.pa %}
      {% if obj4['CodProdus'] == obj['CodProdus'] %}
          {{ obj4['CodProdus'] }}//
          {{ obj4['PA']|round(2)|float}}<br>
          {{(((obj['PretVz']/1.19)-obj4['PA'])/obj4['PA']*100)|round(2)|float}}%
      {% endif %}
   {% endfor %}
{% endfor %}`  

By removing the for loops inside of the main for, it iterates through the entire query, but if i leave the code like in the example below, it only queries 1 item.

来源：https://stackoverflow.com/questions/53602571/querying-multiple-tables-in-flask-using-sqlite3