我正在使用 postgreSQL 进行求和,并希望对结果进行一些计算,但 rails 返回一个字符串而不是 bigdecimal 并拒绝将其转换为 bigdecimal。
create_table SCHEMA_PROJETS + '.proj_charges', :options => 'TABLESPACE ' + TABLESPACE_PROJETS do |t|
# Gem's Reference : https://github.com/lomba/schema_plus
t.integer :proj_sous_projet_id, :null => false, :foreign_key => { :name => SCHEMA_PROJETS + '_proj_charges_proj_sous_projet_id_fkey', :references => SCHEMA_PROJETS + ".proj_sous_projets", :on_delete => :restrict, :on_update => :restrict }
t.string :designation, :null => false, :limit => 60
t.decimal :montant, :null => false, :default => 0, :precision => 18, :scale => 2
t.decimal :tva, :null => false, :default => 8.0, :precision => 5, :scale => 2
t.timestamps
end
这是我的 find_by_sql 和计算代码:
tableau_charges = ProjMesure.find_by_sql ['SELECT sp.id AS "proj_sous_projet_id", SUM(c.montant) AS total FROM proj_charges c JOIN (proj_sous_projets sp JOIN (proj_projets p JOIN (proj_mesures m JOIN proj_paquets_mesures pm ON m.proj_paquet_mesures_id = pm.id AND pm.id = ?) ON p.proj_mesure_id = m.id) ON sp.proj_projet_id = p.id) ON c.proj_sous_projet_id = sp.id GROUP BY sp.id', id.to_i]
tableau_charges.each do |charges|
total_charges += charges.total
end
产生以下错误:
String can't be coerced into BigDecimal
=== 更新 ===
下面的答案给了我一个想法:我的模型 ProjMesure 确实有一个BigDecimal 属性(montant_reference)。因此,我没有用任意名称(总计)命名我的总和,而是使用了 BigDecimal 属性的名称 : SUM(c.montant) AS montant_reference
。
这个技巧可以自动将字符串解析为 BigDecimal。仅当您不打算在查询结果中使用此属性时才有可能。
我的新 SQL 请求:
tableau_charges = ProjMesure.find_by_sql ['SELECT sp.id AS "proj_sous_projet_id", SUM(c.montant) AS montant_reference FROM proj_charges c JOIN (proj_sous_projets sp JOIN (proj_projets p JOIN (proj_mesures m JOIN proj_paquets_mesures pm ON m.proj_paquet_mesures_id = pm.id AND pm.id = ?) ON p.proj_mesure_id = m.id) ON sp.proj_projet_id = p.id) ON c.proj_sous_projet_id = sp.id GROUP BY sp.id', id.to_i]
tableau_charges.each do |charges|
total_charges += charges.montant_reference
end